Has endgame structure changed?

[Senliten]

While all of this is true, this does not mean that they will not invent some new activity to do that rewards gear or tomestones.

What about Palace of the Dead itself? Didn't it come out after Heavensward? Who says they can't/won't do something like that in SB?

I think it is simply too early to say that existing methods are the only way to gear a character up in Endgame when we haven't seen a single Endgame Patch yet, and this is Day One of Stormblood.

IN FACT it isn't even Day One of Stormblood, we're in Early Access still.

I reaalllly don't think they will go that far off the beaten path just yet. Seeing SE likes to play the 'caution game' here, and always have, at least until the class changes.... annnndd i'm sure they are still gonna be processing that for a loooooong long time.
Honestly, PotD aside, the only massive thing known to be coming down the road is Ivalice and Eureka. Both of these are more than likely their primary content of concern to get set and pushed out to meet their expected dates, especially Eureka. So I don't think we will see anything like PoTD till later. Which we might not even see anything new, and just have floors added. So aside from that, it's more than likely the obvious farm for tomes will end up being the same as with SE's previous track record, at least for the start. Whether or not they go even further out into left field with other methods will be up to them, but again, I have my doubts. But as of right now, my money is currently on the same rinse/repeat content, just now in 70's flavor, for the next few weeks.