Despite Fox 20 company owns the rights to X-Men and Fantastic Four. In theory, it is possible that X-Men and Fantastic Four may exist in MCU. If Marvel Studios cooperate with Fox 20 company to make a deal on bringing X-Men and Fantastic Four in the MCU, it will be a wonderful surprise. My personal favorite X-Men member is of course Wolverine/James "Logan" Howlett. Since Hugh Jackman retired the role of Wolverine, there have to be another professional actor that is close to match Hugh Jackman's Wolverine character and carry on the legacy of Wolverine.
In the weblink, https://wegotthiscovered.com/movies/marvel-studios-excited-recastingrebooting-wolverine-mcu/ Marvel Studios is planning to have Wolverine in MCU and is excited to make a reboot of Wolverine. There may be a chance that Wolverine and the other members of X-Men and Fantastic Four will likely be appearing in the Marvel Cinematic Universe (hopefully). I don't know when Marvel Studios will be having a movie or TV series for X-Men and Fantastic Four, but I know Marvel Studios is doing their effort to make X-Men and Fantastic Four special and not bland.