The only thing we know officially is that, when rumors started that Fox had traded the FF rights to Marvel for permission to do X-Men TV shows and a 2020 Marvel FF film was being planned, both Fox and Marvel denied it.
Something dramatic happened in the relationship between Fox and Marvel last fall. Kevin Feige took over responsibilities that Ike Perlmutter had previously managed (And Ike Perlmutter was infamous for his cheapness and dislike of Fox. While we don't know the details, it's likely that Marvel, led by Perlmutter, was in serious negotiations to obtain the FF rights prior to the Trank Fiasco getting started, but they couldn't come to a deal and Perlmutter apparently had issues with Fox after that - reportedly having tantrums, tearing down FF posters and cancelling FF comics to spite Fox).
Shortly after FF failed, we learned of management changes, a deal to allow Fox to make two TV shows and a clear dramatic thawing in the relationship. While Marvel may not have complete control (or they could and they're just waiting for the right time to announce) it seems much more likely than it was previously that Fox and Marvel could (or perhaps already have) come to a sharing agreement similar to the Sony deal - at a minimum.
One thing I found interesting is that after Den of Geek published the rumor, and then denied it, they then published an explanation/apology:
http://www.denofgeek.com/movies/fantastic-four/37400/fantastic-four-den-of-geek-a-letter-to-readers
While the primary purpose of the apology seems to be to explain why they reported something that turned out to be wrong, they emphasize in it that the source they had was reliable.
I think it would be foolish to not assume there's more going on between Fox and Marvel involving these rights than has been made public at this moment.
For Fox to keep the rights, they would have to be in active production within six years from today - and after what happened last time, fans and shareholders might burn down Fox headquarters if that happened.
So Fox either has to come to some agreement with Marvel or lose the rights and get nothing for them.
Based on everything I know, I suspect some agreement has already been reached and we might learn more at Comic-Con. If not, I'll continue counting down the days until Fox loses the rights naturally.
I haven't given up hope that I'll see a decent FF film before I die.