Falcor5 said:
Maybe Spock will be on board the Titan for a diplomatic mission to Romulas after the events of Nemesis. Then Riker gets a message about the attack on the Guardian of forever and the Titan with spock aboard races to the scene. After arriving Spock beams down while the Titan battles to try and reason with the Romulans and he ends up having no choice but to go back in time to save the timeline.
I'd LOVE that! It doesn't have to be a very long scene, but it would be so nice to give at least Riker a proper send off after what they did to him in TATV.
And it would show the non-fan-movie-goer where we are in this particular moment in time, the 24th century. Assuming that they know who Riker is, but I think he's pretty popular among the general public. It would be a nice opportunity to make it clear to everyone that Spock is traveling from the TNG era to the TOS era.