Cinematic rights for F4 and X-Men belong to Fox, Spider-Man comes under Sony and Avengers belongs to Marvel Studios. So the likelihood is that you'll never see Spidey or Ben Grimm team up with the Avengers anytime soon. They all exist in completely different universes. For instance, in Age of Ultron Quicksilver and Scarlet Witch will not be classed as mutants, they're inhumans despite being the offspring of Magneto, who also won't be mentioned because of the licence rights to put them on screen.
And yes, the F4 reboot sounds like a train wreck to me. Even Marvel themselves are distancing themselves from it.