If anything, Obama is the LAST person who would want RP out of the race!
In all likelihood, Romney will get the nomination and give Obama a decent run for his money, but at this point I think Obama's still got it for 2012. One of the reasons for that is that Republicans feel very lukewarm about Romney and yes, Ron Paul has a strong Libertarian following that could take up a couple percentages of the conservative vote. It's become a recurring trend in American presidential races--Ross, Ralph, and Ron, helping out the opposing party a bit. Entertaining, I guess. I actually rather like Ron Paul and think he's made some good points, but yes, some of his ideas are too out of touch with most Americans' reality to grab ahold of the majority of the voting public. Things will have to change dramatically in American politics before a third-party candidate ever gets a shot at the White House.
Will he be assassinated? I guess any political figure is in danger of that to some extent, but I doubt it.