It is looking increasingly likely that Ron Paul will come out of this election the heir apparent to the GOP mantle. It's a toss-up between him and Santorum.
Romney's defeat in November is practically foretold. When choosing a president, Americans always go for the genuine article... this was established in 2004 when they sided with Bush over Kerry. Romney is someone who is so internally conflicted that they cannot understand him... Americans will not vote for someone they cannot understand.
Being next in line doesn't necessarily mean that Paul will win the nomination in 2016. Bobby Jindal has a strong center-right record and a background similar to Obama's. In fact unless someone appears ready to take over for Obama soon, 2016 will be a Republican year.