I've mentioned this in the past, but I've been looking for the avenue the story would take.
The original plan was to spliit Infinity over two films - Gauntlet and War. Avengers would lose at the end of Infinity which requires an Assembling of everyone in the MCU for War. Then JL and Darkseid happened. The Russos are predominantly 80's Marvel guys, so when they took over they convinced Fiege to limit Infinity to one film.
At that point, titles were dropped and it went off radar. Then Strange took a larger role in the MCU with Fiege etc..talking about the gem in Agamotto and how it controls time thereby warping reality. Then over SDCC this drops...
...and that's your road to Secret Wars. Take the Strange Mirror-World, combine it with the other stones making Earth and Battleworld one in the same.
Also, the Russo's just signed a non-MRVL production/distribution deal with Fox. That may be what gets them access to use Jackman, Stewart, Reynolds, Fassbender. And then when you look at scheduling dates, the FF Re-re-boot sits nicely behind the aftermath of Secret Wars.
What's That? Fiege said a MRVL/Fox deal is impossible?
...and what alien race is co-owned by MRVL and Fox?

Skrulls, villains of Captain Marvel movie, set in the 90's. But she also appears in Avengers 4.
So...Secret Wars blows up the MCU leading to an alternate reality where Secret Invasion has taken place. Captain Marvel comes in from that existence. The Nu FF meanwhile...
Franklin and Valeria, two kids deeply connected to alternate reality storylines.
Captain Marvel - March 8, 2019
Unknown Fox Marvel Film Dates - June 7, 2019, November 22, 2019, March 13, 2020, June 26, 2020, October 2, 2020 and March 5, 2021
The original plan was to spliit Infinity over two films - Gauntlet and War. Avengers would lose at the end of Infinity which requires an Assembling of everyone in the MCU for War. Then JL and Darkseid happened. The Russos are predominantly 80's Marvel guys, so when they took over they convinced Fiege to limit Infinity to one film.
At that point, titles were dropped and it went off radar. Then Strange took a larger role in the MCU with Fiege etc..talking about the gem in Agamotto and how it controls time thereby warping reality. Then over SDCC this drops...
“Each gem has its own special power. We had to put a lot of thought into how we would represent those powers so it was clear to the audience. Not only are you dealing with a lot of characters, you are also dealing with the stones, the gems, and there’s a lot of them. So for people to keep track of all of it, we had to get really specific. I won’t divulge how we use the Reality Stone, but we do use it.”
Do you have an idea of what the MCU looks like post Infinity War?
FEIGE: We have an idea yes, and it’s going to be very different
FEIGE: We have an idea yes, and it’s going to be very different
What's That? Fiege said a MRVL/Fox deal is impossible?
“I’ve been at Marvel for 17 years… There are certainly no plans whatsoever for that,” he explained. “But too many amazing things have happened over the past 17 years for me ever say never. But for now, nothing.”
“There’s a chance that aliens could come down from the sky right now,” he countered. “And we’ll use them in the movie in to save money on visual effects.”
“There’s a chance that aliens could come down from the sky right now,” he countered. “And we’ll use them in the movie in to save money on visual effects.”

Skrulls, villains of Captain Marvel movie, set in the 90's. But she also appears in Avengers 4.
So...Secret Wars blows up the MCU leading to an alternate reality where Secret Invasion has taken place. Captain Marvel comes in from that existence. The Nu FF meanwhile...
...the movie swings to the other end of the spectrum. Instead, it will concentrate on Franklin and Valeria, the children of Reed Richards and Susan Storm. While still having the Thing and the Human Torch along for the ride.
Captain Marvel - March 8, 2019
Unknown Fox Marvel Film Dates - June 7, 2019, November 22, 2019, March 13, 2020, June 26, 2020, October 2, 2020 and March 5, 2021