I think D&D, while not exactly becoming more mainstream, is becoming more accepted. There's a D&D club at the middle school my wife teaches at.
I think being nerdy in general is more accepted than it was when I was a kid. Comic book movies are mainstream and super popular. Computers are basically a requirement instead of just something nerds played with when I was little.
I wonder what effect the Big Bang Theory had on this. Because it's only in the last 15 years, during the show's run, as well as Marvel's run of movies that coincided with this acceptance.