>>537450745
It's a toss up between GV and old IP.

BMZ and Bloodstained can be ruled out since Natsume is busy with Majogami

Gal Gun can be ruled out because mainline is on hiatus due to current gay censorship climate and Grim Guardians just got a new game like you said

DMFD is lol, lmao

Gunbike is in Sony jail still

In that tweet, Aizu says: "ヤマトネタが頭に浮かんだのですが" (A Yamato Joke comes to mind), which leans more towards an old IP getting revived as that doesn't fit the description of Gunvolt UNLESS it's something Kirin related. That's if I am not misinterpreting the moonrunes. Now, we do know that a new Gunvolt game is in the works at this point and it'll involve mainline Acura and RoRo. So it's still possible it's that.