I think Joe the Plumber has the right idea. Sarah stays on the outside until after 2012. Then a new GOP president puits her in an appropriate cabinet post (Secy of Energy) so she gains understanding of the nuts and bolts of DC’s machine, and where she has some standing. Then in 2020 after 2 terms of the 2012 winner, she can run.
I think of Reagan's run in 1968, after half a term as governor of California. He could be dismissed then, but 12 years later was able to win. 2020 might be the right time for Sarah Palin...but hopefully after two terms of a conservative Republican President.