Bercow plans to stay on as speaker until after October. What he will do if there is an extension beyond that is unclear, but based on the rationale for staying on, I expect he would stay on through a further extension as well if there was one.

Meanwhile the EU remains clear that the agreement will not be reopened, so anyone hoping to stand for PM based on renegotiating it is either just hoping the EU is bluffing or is asserting they will do something they know they can't.