In the short term, I don't think a lot of people are interested in going to see what would probably be the equivalent of an NBA farm team. Having said that, if the NBA did come here, I think it would definitely cut into UofL's business. As was previously stated there are only so many dollars to go around.
Long term, pro sports rule nationally. I feel like the Colts from the Manning era on were a big hit to IU basketball that used to be king in Indiana. Watered down enthusiasm for college sports might eventually happen here like it has in most places around the country, hurting both UofL and UK.