As exciting as the released X-Men: Days Of Future Past pictures (from Sentinels to Mystique's leg) have been so far, they're also not that surprising. We know to some extent of what we're going to be seeing in the film, as well as what Singer's visual style will be. After all, he directed the first to films in the X-Men universe. Even the footage revealed at SDCC and Fantasia Film Festival seemed exactly like what we thought it would be (not a bad thing). However, there was apparently some other pretty big news that came out of that press conference that was buried underneath the footage shown. Singer reportedly said that he'll be working on a "Marvel movie mash-up" after DoFP.
As you all know by know, Singer's affiliation is with Fox in terms of what characters he can and can not use in the Marvel universe. Still, Singer explicitly referred to his next project will go into crossover territory. That could mean a number of things, but the most likely is that he'll meld the X-Men world with The Fantastic Four or the upcoming X-Force.
Either way, it would make sense to incorporate both of these universes. Since the Fantastic Four appeared in Chris Claremont's original story and the idea of alternate futures (along with time travel) would work perfectly with storylines involving Cable. I personally hope that Fox's property heads into the future (while Marvel heads into space for Phase 3) with a more mechanical, military and sci-fi feel to its properties. Fox would definitely separate themselves from DC and Marvel if they were able to do that.