Legal sports betting could be offered in 32 states within five years if the U.S. Supreme Court rules in favor of New Jersey's quest to offer such gambling, according to a new report.

Eilers & Krejcik Gaming LLC, which tracks state-by-state gambling legislation, says a new market would be worth more than $6 billion. If all 50 states got on board, legal sports betting could be worth $7.1 to $15.8 billion, they estimate.

Americans are already betting up to $60 billion annually using offshore sites and bookies, said Chris Grove, managing director for the firm. It's an industry that generates some $3 billion in revenue each year from U.S. customers.