I suppose one could go with the Legend of Zelda approach where altering the timeline just creates a second parallel timeline coexisting simultaneously with the previous one, which seems to be what the writers suggested. I don't remember that occurring anywhere else in Star Trek though. Indeed, "City on the Edge of Forever," "Yesterday's Enterprise," "Past Tense," First Contact, etc. all use the single-timeline model.
But then, why is the Star Wars Expanded Universe dead now while the Star Trek Prime Universe is still alive? I'd say they're in the same position: still open to new fanwork but no longer active in official productions.