Its an educated guess. We know a few things:
- EA releases a UFC game every 2 yrs or so.
- EA is not likely to release UFC during late July - October to avoid stepping on the Madden, Live, NHL and Fifa releases.
- EA has released UFC games in January, March and June.
So that means its likely that January to early July will be when the game is released. Unless they decide to just wait for the PS5 and release at the end of the year.