It's hard to say but I would gather that Brissett isn't likely to get a lot better than he is right now. He's had 2 full seasons of starting experience plus several seasons being on an NFL roster and his limitations don't seem to be ones that could just be overcome with more experience.
Easton hasn't taken an NFL snap yet.
I am with you I think a Luck comeback is unlikely.
But we wouldn't have to change the deal at all he would just operate under his old deal for 3 years which since we paid all the guaranteed money means there is no guaranteed money left on the contract plus because he essentially froze the deal for a couple years it means he is going to be playing at an insanely cheap rate for a QB of his abilities.
I want this to be true but I just don't think it is.