The Temporal Cold War has made ripples in the timeline. The Romulan time traveler in "Tomorrow and Tomorrow and Tomorrow" strongly hinted that history was at least a little bit different than it had been, with the date of the Eugenics War as case in point. I think the writers are freeing themselves up to make minor changes to canon. I don't think it's a branching timeline, though, it's still Prime. Just a little bit different, like Gabriel Bell being replaced by Captain Sisco.
The Temporal Cold War has made ripples in the timeline. The Romulan time traveler in "Tomorrow and Tomorrow and Tomorrow" strongly hinted that history was at least a little bit different than it had been, with the date of the Eugenics War as case in point. I think the writers are freeing themselves up to make minor changes to canon. I don't think it's a branching timeline, though, it's still Prime. Just a little bit different, like Gabriel Bell being replaced by Captain Sisco.