It's stiill early days, but the odds on favorite for the Reps has to Jeb Bush. The other Rep, however, who may just defy (or vindicate!) the gods is Marco Rubio. Rubio is the only Rep whom both the Establishment and the tea partyers are comfortable with, but it remains to be seen if he has the voice for run. Jeb has the voice, but I wouldn't rule out the tea partyers unifying against him.
For me, it goes in this order of likelihood.
Bush
Rubio
Walker
If Kasich jumps in, do not underestimate him. But I suspect he'll stay out and play for veep.
No other Reps need even bother apply, although they're filling out their applications as we speak. Christie is done, Paul is a known buffoon, Perry is a moron (I know his principal handler and he's alown as well) and you who dream of Palin filling out her application will be sorely disappointed. Even Sean Hannity realizes now the woman is an empty suit twat. A hot twat, but a twat.
On the Dem side, Hillary is as close to having locked up the nomination as is humanly possible. There's always the chance of a shock revelation (I know of one unrevealed shocking truth directly from staff from the Clinton White House, but don't bother asking me) but I just don't see anything that can knock Hillary off the Dem perch.
As for November 2016, stay tuned!