It’s not at all clear that Puerto Rico would be a Democrat state, which is why both parties have steered clear of statehood forever. The Republican party in Puerto Rico has long advocated for statehood. The whole thing is a mess. Puerto Rico is beautiful, well at least before the hurricane, but has incredibly corrupt politics. But with Congress basically running the protectorate what do you expect?
My wife is PR and her family is a pretty even split. When it comes to people still on the Island they are pretty brainwashed by the Spanish media which is very anti Republican. Bet the farm this would mean 2 rat Senators and some rat House members.