It seems likely that it will depend on when the Intel-based 27-inch is withdrawn from sale. Given the late-year replacement cycle for these models, I wouldn't expect much at all until late this year, and if Apple Silicon is going into the revised model, then not much chance of a processor bump in the meantime. If an Mx model isn't on the horizon soon(ish) then the speed bump may happen.
That said, I would personally not expect Apple to do anything with new Intel-based products now. Particularly not if it would cost any product development time and money.