Steve Gillmor has three articles on his blog that give some ideas about where he thinks RSS is going. Whether you agree with Steve or not on the specifics, I'm glad to see the speculation because its expands my thinking. I'm also happy to see more and more people recognizing the power of RSS. When I started blogging, RSS was the thing that got me excited.
Steve claims that email is a subset of the RSS space. That's an interesting thought. Many people might have turned that around. I'd like to hear more from Steve on why he thinks this. I see email and RSS being related in the same sense that email and IM are related. There's a relationship, but I don't see it as a subset relationship. RSS is different than both email and USENET news in a significant way: its self describing. This allows it to be treated as a data stream and filtered, sorted, and merged in ways that we can only dream about with email. If you read Steve's third piece, he hints at this.