Of course they want to become a state now that their "commonwealth" is bankrupt and their professional and educated class are all bailing for a better life on the continental US and elsewhere.
But of course Congress may have other plans as they do not want to be holding the bag for Puerto Rico's financial liabilities.  What would the US gain by admitting Puerto Rico as a state.
Zilch/Nada from what I can tell.  Maybe China might be interested.  They would love to get a toehold in the Caribbean as they are already heavily invested in Central America and South
America under their "soft power" strategy.