When people talk about the US "catching up" to the rest of the world in soccer, they're usually talking about three different things: the progress of American players and the national team, the quality/popularity of MLS, and the overall popularity of the sport (including the WC and foreign leagues).
Those three things don't always go together. Airing EPL and Champions League games in the US has definitely made being a soccer fan easier, but it also makes it that much more obvious that MLS is a lower level of play. American players can probably develop better going through the European club system, but then you don't even have the best domestic players to market your league. I'd expect MLS to keep growing, just on the overall popularity of soccer here, but it's a tricky situation.