If May sticks with the existing timetable, when the Boundary Commission reports in 2018 all the cards will be thrown up in the air and every MP will have to fight for selection for a 2020 GE. All the parties will have 12-18 months to form new constituency organisations out of the existing arrangements, with horsetrading for every position, from chair to ppc. Until it becomes clear where the pinch points will be, every sitting MP has to prepare to fight their neighbours (and allcomers?) for a seat. If/when that happens any MP who isn't well supported will be toast, and they know it.
So the anti Corbyn lot are caught: split now, and spend the next couple of years building a whole new shortterm constituency party and apparatus, as well as collectively trying to assemble national brand, image and presentation (and policies, if they matter). Or don't and... what? With continuing strong opposition in most local, now pro-Corbyn, constituency parties they face a long wait for inevitable career change.
Once the silly season is over, and the party conference has clarified the new balance of forces, many of them will see a pressing need to get their ducks in a row. Mass reconciliation before xmas?