Urianger.

I mean, maybe it's me but he still hasn't fully made up for sending Minfillia to her demise. Yes, it's to save the First and set in motion Shadowbringers, but seems he got off too easy. Felt like they handwaved his consequences by having Minfillia, now Word of the Mother, admit she'd pay that price gladly. He also almost turned the WoL into a sin-eater by going along with the Exarch's plan when that plan went belly up. Then in the Eden raid, he wanted to keep even more secrets regarding the changes after beating the first four battles. Feels like he might need to come to terms with the parts he has played. We'll need a new trust healer at some point. Perhaps Krile could fill that role as a healer trust NPC.

Thancred?
I recall someone posted his tweet about it being his last role. Either he retires or well...
Also noting that Fordola has been getting more screen time in the last two patches, and carries a sword/shield. I "think" she has a half resonant? She'd make a powerful ally and potential Trust to replace a tank slot since without Thancred we have WoL and Graha. One has to wonder if they do retire/kill off a Scion, will it mean they are gone from the Trust roster permanently?

Though maybe we won't see any of them getting killed off, possibly retired or "shelved for a few expansions." After all they did tout post 6.0 it's a new adventure, new (mostly) companions.