I remember the friction between William Shatner and J.J. Abrams before the release of Star Trek reboot in 2009. If I recall, there were some awkward exchanges (and even videos) bandied about regarding Shatner's displeasure with his cameo being cut. For whatever reason he didn't appear in Star Trek Into Darkness either, but now there's a sliver of hope to confuse the timeline even more in Star Trek 3.
Apparently writer/potential director Roberto Orci has written a part for him in the script (with the help of co-writers John D. Payne and Patrick McKay). We already know that this Star Trek movie will actually take place in deep space (as opposed to San Francisco/the CAA courtyard) so it's possibly the good news could keep rolling in.
Per Devin Faraci at Badass Digest:
"I have learned that the script for Star Trek 3 includes a scene that reteams Shatner and Nimoy onscreen as Kirk and Spock for the first time in canon since 1991's Star Trek VI: The Undiscovered Country. It would be a pretty huge moment for fans of the franchise, and likely the last time we'll ever see Shatner as James T. Kirk in official continuity. "
Faraci, who I trust and know to err on the side of caution when posting scoops, continues by saying that "this appearance is plot-driven and integral enough that it might just survive any future revisions."
I'm not sure this would affect the overall quality of the movie either way, but it would be nice for completionists. I'm just hoping this one is less muddled than Star Trek Into Darkness (I liked the original reboot) and enters new territory rather than recycling old stories. There's some speculation that Shatner may decline this part, but I'm betting he leaps at the chance. Why? Here's Exhibit A: