While I'll be surprised if they end up going with the Days of Future Past
storyline for the First Class
sequel, I will admit that seeing Michael Fassbender and Ian McKellen possibly sharing the same frame would be too awesome for words.
Plus, introducing the storyline in the sequel allows the filmmakers a better opportunity to tie this "prequel verse" with the Singer verse. It would also give everyone a chance to see some familiar faces... which I don't think anyone would be adverse to. I'd love to see Patrick Stewart, Ian McKellen, and others again.
Hell, this might be crazy, but perhaps the inclusion of this story could erase X-Men: The Last Stand
from continuity? Maybe that's being too