Even if he decides to bow out at the convention and retire, Ron Paul will be running 3rd party by proxy. He really has no choice. People who choose to write him in come November will ultimately provide the same results of a 3rd party run by Paul.
What I'm saying is...."Ron Paul or NO ONE at all" movement is automatically a 3rd party run with or without Paul being physically in the race.
I hope he wins the nom and if that's not possible, I hope he runs 3rd party. But, if he doesn't, that's ok because I still own my vote and he will get it regardless