Fox has a more contentious relationship with Disney/Marvel than Sony though so that is where most of the opinions that there will be no Marvel/Sony like co-op deal happening come from.
To me it was obvious they was talking to fox for f4 deals for years, so the next option will be sony. Marvel making crazy money but they want certain characters back fox just wasnt going let them borrow f4's characters/villains because the cash cow called x-men but the other superhero they have aren't x-men(ppl rushing to see it) and they will see that
I have a feeling fox will do deal with marvel for the f4 property if they dont live to they standards and if marvel feel like they need reed, sliver surfer and galactus. I dont think marvel wants to do a f4 film but be able to use characters\villans in the MCU. At the same ant man doing good and they might just say fuk it lets do a nova/or cosmo world shift with him with GOTG already in place
My main problem is the way marvel write they villains is lackluster
and the lack of creativity (but I thought "how to steal ant man suit" was a nice mix
But all these companies talk its just deals dont go through most of the time