Assuming that being a Trust does not guarantee a character's survival...

Urianger and Thancred are the most likely to bite it from some kind of heroic last stand or other kind of sacrifice. My money is more on Urianger than Thancred in this case, since the former is big on "do what needs to be done" kind of stuff and I don't see him getting the opportunity to regretfully sacrifice another of his friends. Meanwhile, Thancred had his big self-sacrifice moment, complete with the scene seemingly ending with his death, only to turn up fine moments later. So even if he throws himself into some impossible to survive moment, I don't expect him to actually die from it.

Y'shtola... at this point, I could imagine her pulling yet another Flow stunt, having everyone mope about because she's totally dead for realsies this time, only to have her Unflow herself and drop a fourth wall shattering line about her popularity like Axel from Kingdom Hearts 3.

The twins are safe. Ignoring the WoL for a moment, they are THE protagonists of FFXIV from 2.0 and onward. No amount of "b-but Palom Porom!"-ing from people who never played FFIV will change that. The player is more likely to "die" than they are.

Speaking of things that definitely won't happen because this is not FFIV, the game will briefly become FFIV as Yda pulls a Gaius and shows up alive, overshadowing her sister to the point of rolling her character back to mid-Stormblood. Then she'll sacrifice herself heroically (and turn up alive and bedridden in Little Solace with little explanation) and allow Lyse to have her character development back.

G'raha will be forced to use up all his royal blood magic to do something. The loss of his special eyes will be treated with all the gravitas of an actual death scene, and threads will pop up on Reddit for the remainder of the game's lifetime about how much the scene made them cry because it's Just. So. Sad. This won't actually stop the writers from using his royal blood as a plot device, by the way, since he's stored so much of it in those handy soul popsicles.

Estinien won't betray us. He's done it twice before, and that satisfied his quota as a Kain expy. He's also basically our liaison with whatever dragon-based societies are out there, so they're probably saving his death/near-death for a Meracydia expansion. If anything, I expect him to be the one who gets us to the moon the first time. Dragons can fly in space, after all.

Tataru will not only be alive, but I expect she'll be the leader for whatever group succeeds the Scions in the event that they disband.

Everyone else is fair game. Except Cid. Per tradition, we require him for at least one of the following: Endwalker Raid questline, Endwalker Alliance Raid questline, and Endwalker relic weapon questline.