This kinda reminds me of Hugo Weaving's comments about returning to play the Red Skull.
“I [signed a multi-picture deal] for Captain America. I think the tendency, with those films, would be to probably not bring a villain back. […] And it’s not something I would want to do again. I’m glad I did it. I did sign up for a number of pictures and I suppose, contractually, I would be obliged to, if they forced me to, but they wouldn’t want to force someone to do it, if they didn’t want to. I think I’ve done my dash with that sort of film.”
IMO this set a precedent: yes Disney has the law on their side (signed contracts) but they wouldn't force the actor to do it if they're miserable/hate the experience/whatever the case may be. It doesn't seem to be a case of "Well you'll do it whether you like it or not dammit!" or else we would have gotten Weaving in IW instead of a stand-in.
Bautista is looking at it from the contract side but if he said I'm done I doubt Disney would fight him much on it, if at all.