Not necessary. Shat had his Trek and now the torch has been turned over to a new crew. Spock really is the only decent way of introducing an original member into this timeline. Unless they de-age Shat or something but it's still a pointless undertaking.
I dismiss the whole generations movie anyway. My understanding of the Nexus is that once you are inside it there's no way out. (Do you just walk or swim out?) Once Picard and Kirk were pulled in they went about fixing what had happened to change events. But they are still inside the Nexus so how did they fix anything in real time and get out to enjoy it? It's like the TNG episode where Moriarty tries to free himself the second time from the holodeck. At the end. Picard is holding the holo program thing but inside the program is still running and Moriarty thinks life is going on like normal but he's actually still inside it having no effect on the real world.