IMO, Sarah's path back to relevance would be running for the AK Senate seat in 2014 currently held by a 'Rat. She obviously still has a lot of goodwill among movement conservatives, and should easily be able to put that seat back in GOP hands where it belongs.
No way. Going to the Senate would be an extreme waste of talent. Just ask Sen. Ron Johnson WI. No solutions to problems will ever originate in the Senate.
As far as relevance, Sarah Palin has never lost it. She is as relevant today as she was in '08, perhaps more so. Stay tuned, you'll see.