My early prediction: A primay.
2016 Dem primary would be amazing. I actually think Hillary would be more likely to run in such a scenario (as opposed to her running after an Obama 8-year presidency). The possibilities are endless. Does Biden run? Cuomo? Warner? The good thing for both parties is that they both have a great crop of potential candidates to choose from.
In other words, 2016 can't possibly NEARLY as dull as the 2012 presidential primaries.
If Hillary runs, it'll be as dull as 2000 IMO.