It's all about the Nexus. Somehow, the Nexus dumps Kirk off in the alternate universe. Kirk encounters the new crew in the same manner Spock Prime did in the last movie. Spock Prime left the younger Kirk and Spock a message for Kirk Prime if he ever made his was into the alternate universe. The message tells Kirk Prime he must return to the Nexus because he needs to help Picard stop Soran. However, he also warns Kirk Prime about his death and tells him how to cheat death once again. With the new information, Kirk Prime returns to the Nexus. Then we are left to wonder if Kirk Prime was able to save himself and lives on the 24 Century of the Prime Universe.