Hmmm...I'm afraid, Mr. Chipman, that I have to disagree with you. As more traditional "nerd" sub-culture has been eaten by "popular" culture, so have we delved deeper into our own areas.
Sure, now everybody and their granny plays "video games". But does everyone play Tekken? Or .hack? Or Devil May Cry? Not to my knowledge. Those are examples of "high nerd" software, things that "true nerds only" play.
True, now everyone has a computer. But does everyone know the difference between posting and booting? Can they diagnose computer problems in a command line interface? Nope, in fact, most people over the age of about thirty don't even know what Linux is, despite America's obsession with free shit. That's because, despite Linux being free, it requires a commitment to learning the more complex workings of a computer. Most people just want to type their documents, get software to do their taxes and balance their checkbooks, and maybe browse the Web or play solitaire.
OK, comic book, high fantasy and sci-fi movies are the money-makers for studios nowadays. But how many people who go to see those movies have read Asimov, Heinlein, Chaucer or the various comics and books they are based on? Probably more than I assume (I have a low opinion of humanity in general: as Agent K said, "A person is smart. People are dumb, panicky animals."), but not all of them. How many read the source afterwards? Less than half that hadn't already, I'd bet.
Tabletop games remain firmly nerd-centric, I can think of no-one in my groups who wouldn't be considered a nerd without them.
All things considered, I'd say that Nerd-dom has evolved, turning back on itself even as it becomes more accepted in the mainstream. The entire world has become more nerdy, so we have as well. And that's a good thing.