There's still a long ways to go, but I bet in maybe 30 years the U.S. has a Europe-style 1st Tier/2nd Tier pro soccer format for both women and men with promotion/relegation (on the Europe schedule no less). Lots of likely merging to happen between MLS, USL, NWSL, WPSL Pro, etc. Reminds me of the NFL/AFL situation in the 60's. Bound to happen as competing leagues begin to rise and fall and the market gets bigger. Interesting times!