From whatI can tell, the USA is changing, slowly, they are becoming more open minded about other sports. I've had a few comments in the 3 weeks I've spent here, Miami and in Cancun towards my "rugby" jersey. It is obvious their "rugby" awareness is increasing. Despite the fact Union has a jump start on us here, I don't think there is much snobbery with these newer Union types, and hence I can't see any reason why we can't have an explosion of clubs shortly down the track, with a possible pro league at the top of the pyramid. The AMNRL is doing well and there are regular games on Setanta Sports. The world is becoming a smaller place, sports are growing.
And I agree, from what I hear, the majority of good college athletes give sport away when their pro dream comes to an end. My brother can't get a game of soccer around here, because there are no clubs catering for adults. Adult organised sport is uncommon down here. Maybe this is a massive opportunity for alternative sports to step in.
Take cricket for example, I just went and watched my brother's game in Atlanta today. Who would have thought there would be 20 cricket teams in and around Georgia. And apparently there is 3 or 4 times as many up around New York. They are going that well up there, that they are building specialised cricket facilities.
So yes, I think there is reason to be optimistic about the future of RL and other alternative sports in the USA.