Will we ever go to this Alternate Future?

[Iscah]

We can't perceive a present in which "we" do not exist; ergo any time traveling to the future will necessarily branch off from the present in which "we" do exist. Considering that, we can't visit the Bad Future without some... shenanigans. He does exist in the Bad Future so G'raha can in theory, but even if the conditions were right our limited ability to perceive time makes this prohibitively difficult if not impossible.

Well no, we can't perceive something if we're not there. But going there would involve the "us who exists" travelling to the other timeline, therefore we would arrive there and perceive it for ourselves.

It doesn't matter if the "other us" is there because we aren't going into their body. We are taking our body to their world, whether they're there or not.

Meanwhile, a version of G'raha exists in the other timeline but it is not the same G'raha that would presumably be travelling alongside us. If we arrived prior to "future G'raha" departing to the First, "our G'raha" could come face-to-face with him and they would not be the same physical person.

Again, I don't see how the existance of the other G'raha in the other timeline makes it any more possible for ours to visit the other timeline. They are divided as if by physical space. It's just as hard for either of us to go there.

[Cilia]

Well no, we can't perceive something if we're not there. But going there would involve the "us who exists" travelling to the other timeline, therefore we would arrive there and perceive it for ourselves.

It doesn't matter if the "other us" is there because we aren't going into their body. We are taking our body to their world, whether they're there or not.

Meanwhile, a version of G'raha exists in the other timeline but it is not the same G'raha that would presumably be travelling alongside us. If we arrived prior to "future G'raha" departing to the First, "our G'raha" could come face-to-face with him and they would not be the same physical person.

Again, I don't see how the existance of the other G'raha in the other timeline makes it any more possible for ours to visit the other timeline. They are divided as if by physical space. It's just as hard for either of us to go there.

We can't perceive the Bad Future because we didn't experience it. We can't experience (observe) it since, from our perspective, it exists as nothing more than a possibility that never came to be. Whether or not we physically survived is immaterial.

G'raha, on the other hand, did observe it; it's not just a possibility to him. It's very real from his perspective, therefore he should theoretically be able to return to it.

Time is not easy to navigate moving forward. Out of infinite tessellating possibilities, you'd have to pinpoint the exact one where events played out exactly like they did as G'raha experienced them to get to the Bad Future from which he hails. Our limited ability to perceive time makes this utterly impossible without outside assistance. We didn't experience the events that led to the Eighth Umbral Era, therefore we simply cannot observe the Bad Future from which G'raha as we now know him hails. Thus, going to and interacting with it is impossible as far as we are concerned.

Time travel is complicated, for kupo's sake.

EDIT
tl;dr:

Our perception of time is different from G'raha's. He perceived time as [Bad Future] -> [Good Future], while we only perceived [Good Future]. Therefore by traveling back through his personal time, G'raha should in theory be able to return to the Bad Future. The Bad Future isn't part of our own time, so without an observer we can't go there.

[Iscah]

We can't perceive the Bad Future because we didn't experience it. We can't experience (observe) it since, from our perspective, it exists as nothing more than a possibility that never came to be. Whether or not we physically survived is immaterial.

G'raha, on the other hand, did observe it; it's not just a possibility to him. It's very real from his perspective, therefore he should theoretically be able to return to it.

I am still very confused as to how you are picturing this working.

I think you're picturing that to get to the alternate timeline, we have to travel back to somewhere pre-split and then forward along the other path.

I still don't see how that would have any relevance to the version of ourself that dies in the Eighth Calamity. Travelling back in time doesn't revert us to being our earlier self, but puts a second copy of ourself in that earlier world - otherwise G'raha travelling back from the future wouldn't have arrived in the First to become the Exarch, but would have reverted to being his original self still asleep in the tower. Therefore, the survival of our other self has no bearing on our ability to arrive in, or perceive, the other timeline for ourselves.

The statement that "we didn't experience the events of the other timeline so we can't know what it's like" is... inherent. Of course we haven't had our other self's experience but we wouldn't be needing it because we don't need to travel precisely in their footsteps.

We can't simply get to the other timeline by going back in time and "living through" the split in some deliberate manner to take a chosen path. The split itself creates two copies of us - one who is (and always was) part of the bad timeline and one who is part of the good timeline. And still we are a separate entity to our younger self who is fated to die in the Calamity.

The whole thing is horrendously complicated and I still don't know if I'm even understanding your point or arguing against it correctly because I can't understand how time travel could rely on another self's perception instead of our own action of travelling there.

Also, G'raha observed a very small part of that other timeline, nowhere near the point where they diverge. Anything about the events leading to the Calamity are distant history to him, not something he knows in great detail.

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In any case if they were ever going to do a plot where we visited the other timeline, they might simply invent some kind of new higher power of travel - closer to Omega's direct navigation across the rift - so there would be no need to navigate back and forth through time to get there. Maybe still forth, after we got there. It's all still terribly messy but as long as we only visited a point after soon-to-be-Exarch G'raha left, we wouldn't actually be risking breaking the timeline because by going to the future, not the past, there is no risk of us doing anything that would contradict our knowledge of the past (and thus trigger a split timeline).

Still. I don't think we're doing it in any case because it would be narratively over-fiddly for the sake of going somewhere that is, narratively speaking, better left unvisited. But you're overcomplicating the reason why it wouldn't work.

[Cilia]

The whole thing is horrendously complicated and I still don't know if I'm even understanding your point or arguing against it correctly because I can't understand how time travel could rely on another self's perception instead of our own action of travelling there.

Also, G'raha observed a very small part of that other timeline, nowhere near the point where they diverge. Anything about the events leading to the Calamity are distant history to him, not something he knows in great detail.

You gotta break it down into key events. Things are not as simple as us just going to the Bad Future.

The sequence of events that led to the Bad Future are:

[A] Story plays out through 4.3. None of the Scions' souls are dragged out of their bodies to the First; war with Garlemald goes on.
[B] After making some progress (or even shortly after defeating Elidibus-Zenos), Varis uses Black Rose and triggers the Eighth Umbral Calamity. The PC dies as a result.
[C] Two centuries of labor later, Ironworks survivors open the Crystal Tower and reawaken G'raha.
[D] After retrofitting the Crystal Tower for spacetime travel, G'raha is sent to the First a century ago from its relative perspective.
[E] Midgardsormr awakens and pledges to watch over Biggs III and the rest as they rebuild.

The problem is that [D] messes things up, distorting [A] and negating [B] in its entirely. That sends time down a different path, the "Good Future."

[W] As hostilities with the Empire escalate after 4.3, the Scions souls are gradually dragged out of their bodies by G'raha over to the First.
[X] We fail to defeat Elidibus-Zenos, and are later pulled over to the First by G'raha. Varis elects not to use Black Rose.
[Y] The events of Shadowbringers play out, negating the threat of the Eighth Umbral Calamity and killing the last of the unsundered Ascians.
[Z] G'raha transmigrates from his Crystal Exarch self to his Source self sleeping in the Crystal Tower in the Good Future.

Having experienced the Bad Future (slumbering or otherwise), for G'raha going there would be as easy as moving backward through timespace because he's a part of both timelines. We're not a part of the Bad Future timeline, so we can't perceive it - moving forward will just create another timeline branching off of the Good Future timeline, and unlike G'raha the Bad Future is not part of our (relative) past. We'd need a bridge between the timelines and someone or something with the power to observe our existence in the Bad Future to conceivably go there, neither of which are in ready supply.

Yes, it's complicated. Time is not a simple thing to move backwards or jump forward through.

Suffice to say I also have many, many doubts we'll ever be going to the Bad Future timeline.