But...
Personally I think the biggest danger to the Tea Party could come from within. They seem to want to maintain a focus on fiscal issues and constitutional government, but of course for many conservatives government is about social issues as well: abortion, gay marriage, etc. It represents a huge tug-of-war that's already happening, but which has the potential to get nasty and destructive. Or, to turn the Tea Party into the GOP (in all but name).
Some in the Party have also said that the goal isn't political power, but rather influence. To "change the game." We'll see how long that lasts, especially if power is offered to them.