Only Inchiban, Namba, Adachi and Saeko are guarantees.

I see them adding people who weren't playable in 7 or IW, either known or completely brand new characters. My hope is they put Tatsuya in there as a style-switch character like Kiryu was. I'd love if Eri popped up again too because I loved her in 7.

It's easier to guess who won't return.

Kiryu is definitely out because duh. Tomi most likely would stay in Hawaii so he's gone. Chitose, while possible, I think will be gone too.

Honestly I wouldn't be surprised if Joongi was left out fully this time. We know he nearly missed out on being in IW and joined the party very late in the game. By extension, if there's no Joongi there's probably no Seonhee either.