It's not conveyed particularly overtly (and this has never been a strength of the series), but Kamiya is more or less alluding to what a lot of us seemed to have theorized in the aftermath of the game. There's enough in-game content and postgame content to imply that we haven't seen the last of Cereza by a long shot, even if it's going to be Viola's story from here on out.
I'm still holding onto my theory that it's going to be a Viola protagonist joint through the Fairie world, and that their version of Cereza, or maybe even Jeanne, will be the secondary playable character this time. New generation, brand new means of character development, hopefully an opportunity to dial back a bit on having to one-up its insane escalation.
The way he talks about Bayonetta 4 makes me wonder if it is planned to be delivered on a much shorter timetable. What if we get it in a couple of years?
Otherwise, I'd honestly prefer a DLC campaign first.
Platinum apparently pitched Bayonetta 3 around the time that Nintendo commissioned them for the Switch ports of 1 and 2. To me that implies that after Bayonetta 2, it didn't sound like they were too gung-ho about jumping headlong into the next entry. Kamiya was busy with Scalebound at the time and Nintendo's production team commissioned them to make a new IP with Astral Chain. Compared to back then it sounds like Kamiya and team had a
lot of ideas during Bayonetta 3's development on what the franchise will be doing next and after playing the game it's definitely chock-full of stuff to build on. Half of the game's story is ostensibly dedicated to brand new world building that isn't paid off in this entry but sure seems like it's going to be hugely important in the next.