Rumors are flying fast and furious regarding 2013 sets. We should be seeing the first set images in the next few weeks, but in the interim this is what is shaping up:
Teenage Mutant Ninja Turtles looks like it will indeed be the next licensed theme, starting in January?
Lone Ranger could be the following licensed theme for Summer 2013, as part of the overall Disney-LEGO agreement.
Legends of Chima could be the next big "action" theme from LEGO. Rumors are that the characters will sport animal heads and will have vehicles that can be powered by ripcords.
Ninjago isn't dead yet, with at least sets for the 1st half of 2013 in the works.
What was originally thought to be a Polar exploration theme "Polar Express" is actually a space theme "Galaxy Squad" which seems to involve space marines who go to hostile planets (one of them being an Ice Planet).
The City theme is going back to firefighters again, with a new station, fire truck, etc, including a "residential house on fire" - that could be interesting. Also keeping up with the LEGO City police state, there may be a new SWAT subtheme, which includes a "museum heist" set. Hmmmm...
It won't be much longer until these rumors are either debunked or validated.