I mean we're 100% getting a new cast after Secret Wars. It's possible they even show up in this movie, but Doomsday, which sets up Secret Wars, is meant to be one last adventure before a soft reset. The next phase of Marvel films is mutants and the X-Men.

And yes, we've had one last adventure for X-Men more than once. X-Men 3 ended the trilogy. Days of Future past reset the timeline. Logan showed us the end. Deadpool 3 credits had a full end of mutant saga retrospective.

So is this one really the last one? Yes. (But never say never to a future cameo, but main story, yes.)