The NIGC reports combined gaming revenues for all US tribes of $25 billion. That represents almost 11% growth since just last year. Also, that $25B was earned in just 415 tribal gaming facilities.
A considerable amount of research suggests the industry is not even close to the saturation point and has nowhere to go but up.
Frankly, I think it's great because the tribes spend that money to help their people and they spend it locally.