The problem will be displacing Romney in 2016 (assuming he wins in November). If Romney is elected, there is almost a 100% chance he will also be the nominee in 2016 - unless he decides not to run for a second term, a remote possibility as he will be 73 years old. But if that happens, Paul Ryan will have the inside track.
The only way the door will be open for Sarah Palin to run in 2016 is if Romney/Ryan lose and as much as Sarah Palin fan as I am, I do not want to see that scenario.