I think a split should occur as a result of Spock trying to fix things and that will leave our TOS and the rest of history as it is, and allow for the offshoot to grow and have its own history to be recorded. Then we can watch this crew grow and gel and gain a place in Star Trek all their own.
If time is a river, then that never-ending flow will carve out new paths all the time. Even the Mirror Universe, with all of its premature deaths of key figures, still manages to parallel the ST timeline over several centuries and resemble a similar environment and population.
Remember in "Yesteryear" (TAS), where Spock, as Cousin Selek, manages to restored the damaged timeline, only to realise that a minor change had occurred: his pet sehlat died during Young Spock's practice-run at the kahs-wan, instead of living to an even older age. As Spock observes in the episode, it is perhaps an insignificance which may matter to some.
If Nero's tinkering with the timeline causes changes, I'd expect most of the familar order of events to eventually reassert themselves anyway, with no need for the pressing of a reset button.