Vulcan is gone and as a result the Federation is notably weaker. The Klingons have lost 47 ships. The Romulans (probably) know, really know, their planet is destroyed in the future. Old Spock is around to ward off future catastrophies, like Khan or V'ger or the Whale Probe.
Time for new stories. Romulans swarm out of their empire? Klingons seek revenge on the Romulans for the destruction? Let's go.