There's an article on the Time website (don't know if it's in the print edition) musing about why fantasy movies have been getting more successful, but Dungeons & Dragons has kind of been languishing as a fringe activity. Of course, I've seen some people comment on this already, suggesting that they'd hate it if D&D became more mainstream, because they like the fringe aspect of D&D. You can't like something if lots of other people like it, right?
But I'm not really going to talk about elitist attitudes like that. I want to address the question in the article: Will Dungeons & Dragons become more popular and break out ifs sense of isolation? I think the question ties into the same distrust of system issues I've raised before, including the recent examples of buff spells we've been discussing. It may sound absurd, but I think that as long as there are buff spells and things like them, you aren't going to see D&D getting more mainstream appeal.
See, the Time article puts forth the idea that, since The Lord of the Rings movies are popular and The Game of Thrones TV series is popular and it looks like The Hobbit is going to be popular, Dungeons & Dragons ought to be more popular; after all, it's got the same themes, the same tropes. But, as the article goes on to explore, D&D is a whole lot more than just playing in a fantasy world, or at least it has become more than that. The dominant strain of D&D right now is, as the article puts it, obsessed with "Endless streams of books filled with classifications and measurements". It has become focused on system master and system tweaking, instead of on having a fantasy adventure.
Maybe I'm just crazy, but I think most mainstream people dislike obsessing over the guts of a game system. They see something like The Hobbit and think "man, it's fun to think about adventuring in a fantasy world," and then they look at D&D and see that it's currently about finding the best character build and learning about synergistic power combos -- in other words, it isn't about the same thing at all.
And I'm not even going to get into the whole isolationist/paranoid mindset of many groups, or their disdain for people who don't learn all the rules and use them to maximum effect.