I hesitate to bring this up, but I think a new character is guaranteed. With Fishburne departing, that leaves the entire main cast as all Caucasian. That means they're going to have to bring in someone to make the cast more diverse. I personally would love to see Aisha Tyler return, but that is highly unlikely. As for the fear of Sofia taking away from Brass should she return, not necessarily. If they go back to working more than one case an episode, then they could have Sofia and Brass on two different cases. Like in seasons 6 and 7. And should Marg leave, Vartann might be seen less or disappear entirely. And other detectives are rarely seen now, given the current one-case-an-ep formula.