If he has stateside income, yes. For example, my investments are handled by a mainland broker, USAA, they issue a 1099 and I have to fill my 1040. Every year. When I did consulting work and traveled to the mainland on business and got paid there, I had to pay Federal Income Tax. My wife's rental property in the maninland pays federal income tax. And that's just me.
You'll correct me if I'm wrong, but PR state taxes are quite high if you have a good income, so if you move to PR thinking you're going to get a break on taxes, you'll get a surprise.
I was considering staying, and it looked to me as if my taxes would be similar living on the island to what they are now, with US federal and my state tax.
You will probably gather that I favor statehood for PR, but not directed by some judge somewhere. The attitudes of the people I worked with would not be necessarily representative, since they were relatively few, but my impression was that they valued their US citizenship highly, but feared statehood for fear that they would lose their uniqueness somehow if they accepted full statehood.
They look across at Dominican Republic, or these days at Venezuela, and think there but for the grace of God and the US go I... but they still value their identity as Latin Americans in addition to their identity as US citizens.
But since you are from there, and breathe their reality on a daily basis, I value your opinion. I'm curious about your comment that the current territorial status favors the elite more than the average folks; that may be true but I would be curious to know some examples.
By the way, my understanding is that the tax breaks that originally brought manufacturers to the island have been discontinued, and PR must compete for manufacturing on a rather difficult playing field. NAFTA and CAFTA means PR must now compete with Mexico and the rest of Central America. Being 1000 miles from the mainland, at a distance from both suppliers and customers, makes it tough. But those industries already on the island seem prepared to stay for now (except for oil refining which is now mostly gone).