Why not do both? X4/First Class... Combine The Franchises!
I see a thread about X4 and about a First Class sequel but why not do both at the same time in the same movie?
Given the critical praise but light box office of First Class and the love of the trilogy by most, it makes the most sense for Fox.
For me, First Class/X1/X2 is now the X-Men trilogy with X3 as a side note. Those three films are now THE best trilogy the genre has delivered. So...
X4 = Days of Future Past with BOTH casts!!!
Old Xavier (Patrick Stewart) contacts young Xavier (James McAvoy) to save the world! Logan (Hugh Jackman) can stay the same age but use different actors for the same characters in both time periods!!!!! Fassbender plays off Sir Ian and we get a younger Storm and Cyclops plus real Sentinel attacks. Killing Logan and Storm and Peter in the future would make for great cinema and that way the old cast can hand the franchise off to the new cast in a cool fashion. Restore the box office glory and we all win.