No way should there be a rematch. Povetkin is only going to get worse and Joshua is going to improve further.
I'd watch a rematch as it was ultra competitive and enjoyable, however like others have said, it will only be worse next time out for Povetkin. I'd rather see him face Wilder, Ortiz, Fury or Parker. All very winnable fights, especially Wilder and Ortiz. Fury and Parker less so stylistically as they move a lot more.