If a potential new state has a relatively heavily (say 60%+) lean then it'll never be admitted unless steps are taken to balance it out. Like how certain subdividing of California could. Unless the Democrats have a supermajority in both houses, and the President, and they actually get their heads out of their asses enough to get something done, I doubt Puerto Rico will ever get statehood. They might want to kick out the overrepresented continental real estate assholes first.