They're already US citizens and are pretty much treated as a state in most situations. It makes sense. If they choose statehood in the referendum, I think Congress will act pretty quickly to set them on a path to statehood. But there will be some awkward situations, especially over their seats in the house (a couple states will end up having to give up a seat) and I guarantee you over spanish being such a dominant language.
Honestly though, I'm impressed with most politicians on the issue. We'll see if it survives the election. I think it'd be good. A little diversity is always good, and hey - it's pretty cool to add a new state.