If it did happen, Romney's choice would still win. Paul and Romney have a cozy relationship, if Paul really has any influence, things will be taken into account before Romney announces his choice.
The only reason that the Paul-Father isn't running 3rd party is because of Rand's future in the party. But Ron hasn't even endorsed Romney. They really aren't close, Paul had a lot of attack ads on Romney but the media didn't really cover them. And Paul hasn't even endorsed Romney and is having a shadow convention the day before the RNC.
Paul attacked Romney, and Romney attacked Paul throughout the race. But Romney is at least willing to hear out Paul, even if he does not change a thing. Thats why Paul likes Romney so much. It is not a "shadow" convention like the last one-its a simple festival. Maybe he will announce his endorsement of Romney/Johnson/Goode/nobody at the festival?
Paul will likely get a speaking slot-especially if he is declared the winner in Louisiana, in which he would be allowed to be placed in consideration. If that does not happen, Romney will want to shore up the Paulites like me, by granting Paul a speaking slot, even if he does not endorse Romney in particular.