The chances that there will be a 51st state in the near future are reasonably good. Whether it will be a territory on the moon, or Puerto Rico, is uncertain, although the odds heavily favor Puerto Rico.
As a Puerto Rican, I find it amusing when the U.S. tries to instruct other nations in the practice of democracy (See: Libya and Iraq). Before the U.S. instructs other nations on the practice of democracy, it must re-think its policy in Puerto Rico.
A new bill is designed to craft an artificial majority for statehood where none exists now. Every time the people of Puerto Rico have been consulted on this issue through a plebiscite they've said no to Statehood.
The main argument against Puerto Rican statehood is taxation. Except for DC, it has been the policy of the federal government that there be no taxation without representation, so Puerto Ricans don't pay income tax.