I think there was some talk that Bellew could try and go after the winner of the Cruiserweight super series winner, aiming to become he unified champion if he won, but that would be several fights away against some really dangerous people. I don't think he intends to be around much longer and a second decisive win over Haye would be a good end to his career I think.
Haye I don't believe wants anything to do with the likes of AJ & Wilder, they're just too dangerous for him at this stage. He seems very different in the build up to this second fight, perhaps realizing he's no longer the fighter he once was due to his time away and injuries. I think anything other than an obliteration of Bellew and his career is done too. If he does spark Bellew out then something like Tyson Fury (providing he come back with no issues) would still be a pretty big fight to make. There's plenty of history and bad blood between them that I'm sure a lot of people would like to see resolved.