Considering the current circumstances FWIW, I have some predictions to make:
1. May steps down as leader some time as early August, allowing time for a new leader to be elected by the Tory conference in September. The new leader is a surprise, and has either not had a major cabinet role in the past or is a young backbencher.
2. Corbyn carries on riding high in the polls until the new leader emerges, at which time the new PM will get a bump.
3. The new PM will use conference and the reaction to themselves as PM as the deciding factor on if to go ahead with a snap election.
4. Stormont and Brexit are difficult to call. I think May will probably do everything possible to get Stormont working, because a flaring up of violence in NI during the marching season and the imposition of direct rule is a wombo combo that nobody in their right minds would do. Given the government's Brexit plan is, as far as any commentator can tell, to walk out of negotiations, they are up a creek without a paddle. As we start knocking months more off the schedule, this is something the public might begin to get very nervous about.
So here's some scenarios:
1. May manages to do Stormont, the Queen's Speech and the first chunk of Brexit talks amazingly well. This allows her to hold on as PM.
1a. The above does not happen but out of 300 plus MPs there is exactly nobody who wants the job so she clings on anyway.
2. May goes in August, we get a surprise new PM and that PM thinks they can beat Corbyn in a GE. Parliament reconvenes after the conference season. Labour really want another election and the Tories might be emboldened by a new leader.
2a. The new leader is Hammond, BoJo or another of the badly-smeared May cabinet and take over as caretaker PM. They do not call a GE and Corbyn and McDonnell have to keep the momentum going for two years, which could be hard.
So at this point it all depends on when May steps down, who replaces her and how good a choice that is. It is critical for the Tories, if they wish to remain in power, to find a serious alternative, likely someone young, who can beat Corbyn. But I am seriously struggling to think of someone who can do that.