According to someone on Twitter, "le nouveau Final Fantasy de Square Enix n'est autre qu'un Souls-like"—that is, "the new Final Fantasy from Square Enix is nothing other than a Souls-like."
Of course, I wouldn't share just any claims from mysterious French-speakers who go by SoulsHunt. This rumor has some backing: Fanbyte says it has sources who confirm the rumor's truth, and that the game may be called "Final Fantasy Origin."
According to Fanybyte, Origin "appears to be" a PlayStation 5 exclusive, but will get a PC release sometime after the PS5 release. Both Fanbyte and the Twitter leaker say that it's in development by Team Ninja, and that it will be similar to Nioh—in other words, a bit like Dark Souls. (Specifically, Fanbyte says it's being made by the Team Ninja group that developed Dissidia Final Fantasy NT, a group which some Nioh devs were shuffled into.) Fanbyte also says that the game will be "more accessible" than others in the genre, and SoulsHunt says that, unlike the Dark Souls games, it will have difficulty settings.
Final Fantasy Origin is reportedly part of Square Enix's E3 showing, so we should have details direct from the source in June—if it exists, at least. I don't have any sources of my own to confirm the rumor, but it's hardly far-fetched that Team Ninja would be working on another Final Fantasy game.
We do know for sure that Square Enix is participating in E3 2021, although the company hasn't announced a date for a livestream yet. When it does, you'll find it in our E3 2021 press conference schedule (with only a couple complete announcements so far, it's a work in progress).