Paul conceivably had a chance when the field was full of neocons during an unpopular war. Other candidates dropping out hurts his chances, which have dropped to zero. Romney dropping out eliminates the chances of having any significant influence at the convention. Paul may continue until the convention in an effort to promote his message or set himself up to bring the Libertarian Party a record percentage of the vote by running as their candidate.
The big mistake of his campaign has been going after the Republican vote by emphasizing how pro-life and so-forth he is when they should have been emphasizing the things that made him stand out and draw the college crowds in the first place. It wouldn't have been enough as things turned out, but it would have been a more interesting ride. If Paul still has something up his sleeve that will make a difference, I can't see it. At least he actually picked up some delegates and broke 20% in some states, that's better than anyone not on board with him thought he would do.
Paul supporters, I love you, I am even (reluctantly at times) one of you. It's not a conspiracy, this is what primaries do. It turns out the longshot with little money who comes out to be the big winner happens to be McCain. Let it go. If you vote Libertarian, it will make you feel better, or at least it will help you get used to the feeling of your guy being soundly trounced.