I think a more likely scenario (not LIKELY...just MORE likely...which is different...still it would be a slim chance) would be the GOP moves left, and the Dems STAY left...and then the West and Southern states develop some sort of a cobbled together 3rd conservative party.
Sort of a flipping of the UK Labor, Tories, Liberals where the Dems are Labor, the GOP Tories and the new conservative party is sort of like the liberals.
Of course, it wouldn’t really do much good, but I can see the Dems staying so far left, and the GOP moving left to pick up the Fiscal conservatives who are socially liberal, and then the tea party types create a 3rd party based in the South and West.
It would take some kind of wedge issue where people were so ticked off they left no matter the consequences on national elections.
Again...very unlikely, but not impossible going forward.