Yea because general audiences and critics alike absolutely LOATHED the DOFP that we got. Oh wait...
Ok I'll bite. Vaughn returns to direct his sequel to FC. Everyone from his original film comes back. The only "new" face is Wolverine. Played by Tom Hardy (for some reason). Set a decade later. All of this he's been on record as saying was part of his plans.
Say his sequel does well and Fox allows him to do a third movie, his Days of Future Past. Tom Hardy returns to play Wolverine? Who plays the older Xavier, Magneto, Storm, Iceman, Rogue, Kitty, Colossus, etc? Do Stewart, McKellen, Berry, Ashmore, Paquin, Page, Cudmore, etc return? Wait, but why? And if they don't return, where's the emotional investment?
Yea, this is dumb. Almost as dumb as making Mystique Xavier's sister.