Given all the bad rep Brave seems to be getting I would assume they would show up. Hell some of the V4Mirai girls seem to be invited. Holo probably also have some karaoke/concert and meet and greets probably because it will cost them nothing and having them on will "legitimize" the event more. They could probably even set up a small booth and get some of the exclusive left-over merch over to sell. Shit like what they sell in the Tokyo Station Shop which is mostly exclusive and you cant get unless you buy from scalpers or you physically travel to Japan. Niji's rep doesnt seem to be completely in the shitter so I would assume they might have a small booth to promote their new wave too.Yeah, I don't think they'll miss out on having guests there, the question is if they'll pay for the privilege like Phase and V-Dere have for example.
I don't think Holo has to, they could probably be exempt from the "no two years in a row" rule without paying as well. But I think Brave might like to boost their presence a bit by sponsoring some part of the event.
Offkai is basically the "big" Vtuber convention in the US and like all other convention, it seems to be full of the same moral faggots that end up ruining every single space. Next year we can expect the furry vtubers and the piss-filled ballpit.