As for me, I don't care what the plot is about as long as they
a) Don't bring forward any TNG stuff like Q or the Borg, and
b) Have a good old-fashioned Bones vs. Spock scene. Honestly, one of the most famous friendly rivalries in fiction, and Urban and Quinto have barely said a dozen lines to each other.
If I had to predict the movie, I'd say that they'd adapt an unproduced mirror universe based two-parter from the death throes of Enterprise, where Shatner would return as an elderly mirror-Kirk.
The Reeves-Stevenses, who had the idea for the episode, said...
It seems like the sort of thing Team Abrams would love."The idea was that the Tantalus field was not a disintegrator, it was a humane way of dealing with prisoners, by sending them back in time to a sealed penal colony. Enterprise (NX-01) comes upon the colony – and Tiberius [mirror-Kirk] is there. Tiberius thinks, 'Finally, a ship with a transporter – I can get back to my own universe, my own time.' He basically goes on the NX-01, gets to the transporter, sets it to go back to the mirror universe – the mirror universe doesn't exist - it hasn't been created yet. So Tiberius and Archer work together to figure out where the division point is between the universes, what point that one split off into the other. And as it turns out, Tiberius and Archer together are responsible for the creation of the mirror universe."