From the article:
“On the criticism that Puerto Rico will just become another blue state: “There is no real evidence. We just had a Republican governor, a Republican House and Senate. Puerto Ricans are socially very conservative. Frankly it can go either way. If the Republicans were to play their cards right, it could become a reliably red state. Remember the history. Everyone thought that Alaska would be the Democratic state and Hawaii would be the Republican state. Look what happened there.”
About Alaska and Hawaii: it's an interesting point. I don't think that everybody didn't say that, but you might have made an assumption 50 years ago that Alaska would follow other recently frontier states like Arizona or Montana, and at that time Arizona was solidly Democrat and Montana strongly tilted that way in Congressional elections. As for Hawaii, most of the Representatives in the territorial period were Republicans, as was one of the first Senators, Hiram Fong. So it's entirely possible that someone making a prediction back then would have gotten it wrong.
The difference between then, and now, though, is that politics is less determined by local issues and more by ideology. Old ethnic and religious tensions and conflicts aren't as much of a factor as they once were, but evangelical vs. non-evangelical and white vs. non-white did a lot to decide how people voted in the last election, and unless a lot more Puerto Ricans go evangelical very soon, we know what the numbers will mean. There may be a few surprises, but I think we pretty much know what the trend will be.
Unfortunately, said GOP Governor just lost reelection and the Resident Commissioner is a Democrat. Add in the language situation, the per capita income, a full-throttle race baiting by the national Dem party and with the formal organization of the parties and PR would likely become a slightly more Conservative version of Hawaii. The GOP would be crazy to support statehood at the present time.