While we should expect a few years to pass before the latter franchise is adapted for the MCU, Phase Four seems like a likely place to finally bring the Fantastic Four into the fray.
The MCU is still expected to grow substantially in Phase Four, especially considering Disney+ and the merger between Fox and the House of Mouse.
With Disney now acquiring 20th Century Fox’s assets, Marvel finally has control over the Fantastic Four and X-Men characters.
Especially considering how dismal the last attempt at adapting that team of heroes went.