I never believed for one minute Fox/Marvel would collaborate on anything FF related. Maybe Xmen perhaps? Any deal made would involve characters back into Marvel fold and some concessions to Fox. They wouldn't inform us of that anymore than Feige telling us they just got the rights to Ego before it happened.
Fox are not in anything like the trouble Sony was, so unless they 'do a Sony' with their X-Verse moving forwards (making them continuing alone untenable...Hello Simon...) any 'partnership' seems highly unlikely at best.
It's not inconceivable they
might go for a one off 'Avengers Vs X-Men' crossover in the future (like
several years from now, an alternate world crossover thing like the TV series Flash & Supergirl), but that's are far as I can see either being willing to go. I wouldn't consider that option likely either tbh, but it is at least a possibility they
might consider down the line. As things stand atm? I think Fox will continue alone with all things X-Men for a good while yet.
Fantastic Four is fubared big time with Fox though. Wouldn't help them out for one second after they messed them up so bad....Could just imagine that desperate phone call...
Kinberg: "Hi Kevin, listen, we really need your help with the FF. We know we ###ked up bad, but we really really wanna reboot them into your MCU. You call all the shots, well most of them, but we keep the rights. That ok by you?"
Feige: "April Fool come early has it?"
Kinberg: "I'm serious dude, I already wrote a screenplay. RDJ will love what I've done with Stark. He's gonna get drunk on a few sips from a hip flask, be fused to his iron-man suit and be able to blow peoples heads off just by looking at them. It'll be awesome!!"
Feige: "That sounds uncomfortably familiar Simon....What about the FF?"
Kinberg: "Who cares about them? We get RDJ and the MCU!!"
Feige: " Simon...I have to go, I have another call...."
Kinberg: "You really don't do you? You're just being polite before hanging up."
Feige: "And there I was thinking you were a complete idiot. You're just mostly an idiot. Have fun trying to convince Fox shareholders another FF film is worthwhile, bye now."
Kinberg: "But RDJ!!" We need his goatee...pleeeeasse!! Kevin? You still there?....Kevin?" ....Aww ###k it."