If DoFP grosses 8-900 million and Singer wants to do an Apocalypse story, I would do two films back to back and tackle that story, as he would have structured X3 and X4 with the The Phoenix. I agree I don't think you can do that story with a younger take of these characters. It just won't work putting new up and coming actors against something like that. Unfortunately, I think that means the end of the FC cast, and I doubt Fox could bring them back to reprise their roles in the future if they are cast off to the side in favor of X-4/5. I say Sinister and Apocalypse can wait.