There are several Labour MPs who are potential future leaders of the Labour Party, just biding their time in other roles until we see what happens with Corbyn. Three have been named on here, Starmer, Burnham and Cooper. Personally I would choose Starmer, but I think it will be Burnham. It won't be Cooper. Angela Rayner could be a dark horse. Rebecca Long-Bailey is one to watch for the future. It will be someone who is a better orator than Corbyn, but supports his policies.
Personally I don't have any gut feeling how much longer Corbyn will remain leader. I'm not sure if he will try to win another election, but nothing indicates his position is in jeopardy. It has crossed my mind he will stay long enough to ensure the contents of the next manifesto, but not necessarily be the leader at election time. It's a weird situation.