I think it's still a dynamic and interesting field, and there are still good tech articles on HN's front page every day. I firmly believe that we are still in the wild-west of programming as a profession, and anyone who says they know what the next twenty years will look like is delusional.
The problem here is simply dilution. Every niche social site that grows large will eventually face the Eternal September, when the userbase grows too large for moderation, and the content drifts dramatically. At that point you simply have to move on and find somewhere that still has a focus on the topic you originally were looking for.