support themselves financially, and see how it goes. If there actually is demand for your product, then the public will pay to keep you going. If not, you will sink into oblivion, and deservedly so.
The USWNT could possibly make a go of it, given that they actually have fans and can draw a TV audience - although their numbers are still relatively small compared to most "big money" sports, and they don't draw consistently (mostly America pays attention during the Olympics and the Women's World Cup, and then quit caring for the remaining 90% of the time).
But yeah, the WNBA would crash and burn almost immediately without support from the NBA. That would sad and yet somewhat amusing at the same time.