Nate Silver points out that Santorum is effectively blocked from seeking statewide federal office in Pennsylvania which means his future is up in the air:

Mr. Santorum could also look to statewide office in Pennsylvania, but that might require a reasonably long wait. The incumbent governor there, Tom Corbett, is a Republican and is eligible for another term in 2014, so Mr. Santorum would either need to mount a primary challenge or hope that Mr. Corbett retires.

Of Pennsylvania's two incumbent senators, one is a Democrat, Bob Casey, who resoundingly defeated Mr. Santorum in 2006 and who remains fairly popular. Because Mr. Casey is on the ballot again this year and it is too late for Mr. Santorum to challenge him, he would need to wait until 2018 for a rematch. Pennsylvania's other incumbent senator, Pat Toomey, will be up for election in 2016. But Mr. Toomey is a Republican who is relatively young and who is too conservative to be vulnerable to a primary challenge.

Mr. Santorum is himself fairly young at 53, so he will have plenty of time to build up his brand name and evaluate his options. Still, it could easily be that the 2012 nomination campaign will prove to be the high-water mark of his political career.

If Romney wins in November, Santorum would have to wait until 2020 to run for president again. But as Nate points out, some heavy hitting Republicans like Chris Christie, Bobby Jindal, Paul Ryan, and Jeb Bush would all still be young enough to run. Santorum might get lost in that field unless he is able to keep active in national politics.

He would make an excellent party chairman if the GOP wants to please conservatives. Beyond that, he might keep his hand in by running in 2014 for statewide office as state treasurer or attorney general, and then mount a challenge to Casey in 2018.

The immediate future is less cloudy. Santorum will almost certainly go to Tampa looking to impact the GOP platform - at least on social issues. And he will get a prime time speaking spot, perhaps on the opening night of the convention.

Rick Santorum isn't going to disappear anytime soon.