The truth is that RSS was a cool technology searching for a reason to exist. It managed to find it on occasions (podcasting is still alive, twitter basically used RSS as the "first draft" for their service, etc) but not in the big way most geeks thought it would. Commercial and user interests did not align with a vision of complete openness where standardized feeds get pushed from machine to machine, moving free and public content everywhere. Also, most services found the format to be a straight-jacket, and once you start adding custom namespaces, you might as well just use your own format. It fit well only for periodically-updated news/blog sites, which is what it was built for. And its worst sin is that it's fundamentally a one-way technology, a broadcasting tool, not a bi-directional tool. Social tools can be built on top of it, but at that point it becomes just another messaging format, and not particularly efficient either.
RSS will survive in some form (like RDF, remember that?) but will never gain widespread popularity, unless it's somehow reinvented in a way that will align with the interests of big commercial players and/or large number of users -- something we failed to do in the last 10+ years.