Avengers: Endgame might see the merging of the two personalities into Professor Hulk, which would may keep the character alive, but keep Ruffalo off-screen.
With that said, it’s interesting to think of what the final part of Hulk’s character arc may be.
Hulk could also die, although we’re hoping Marvel won’t “smash” our hearts like that.
Thor: Ragnarok established Hulk as a separate person and Avengers: Infinity War showed Bruce stepping up to fight when Hulk was too afraid.