I still think they'll go with the Klingon War thing started in STID. The setup was there, all they have to do is flesh it out.
Hostilities arise on the border, and the E is sent to intervene. Young Kirk, with his experience and newfound wisdom gained through loss and introspection, settles the conflict with cunning and wit.
Spock, after tiring of flying off the handle at every opportunity, ends his relationship with Uhura and becomes the more stoic character we expect.
Scotty throws Keenser out an airlock, reducing his stress level and propensity for outbursts.
Sulu finds a hobby in the botanical gardens.
Chekov finally is old enough to buy vodka from the ships stores, and spends his spare time telling stories about ancient Russia's technological advancements, including a little old man from St. Petersburg who inwented the light bulb.
McCoy tries to curb his tendency for metaphor, and starts to hang out on the bridge for no apparent reason. He is unsuccessful, but it is a gallant effort.
Uhura will reluctantly give up her pursuit of Spock, and relegate herself to "answering the phone." She will also forget how to speak Klingon.
And that will finally be the perfect NuTrek movie, a grand sendoff to this cast. Ready for the next reboot.