To me, what's most interesting about this development is that the new top of the ladder is being taken by a "global" sport, basketball. Basketball ranks 2nd in world population only to soccer/football... I grew up with basketball and it was not really thought of as an "American" sport.

As a European native who's lived in the US for over 30 years, I always found it interesting how "US-centric" sports were, here. One of the things I picked up on here-- already in college-- is the popularity of sports in the US being strongly linked to their natural integration with commercial TV. A lot of people have theorized that soccer was never popular in the US because (a) it's played for 45 minutes a half without interruptions (no chance for commercials) and (b) the US doesn't like sports that often end in a draw.

Just guessing here, but I would think the slow decline of US Football could be tied to the advent of the Internet... we're becoming a global community, so uptrends are more likely to happen in sports that are seen worldwide, while the importance of "local/country" sports will decline.