It all makes me laugh.
First of all, I've never even been to Comic-Con and I know that it's no longer really about comics anymore, and hasn't been for some years, so I don't think another media event for yet another fantasy blockbuster is all that much of a sea change.
Second, and more importantly, nerds need to get it through their heads that there is no hierarchy of fandom, much as everyone likes to pretend there is (and isn't it funny that no one can agree who belongs on the top of this mythical dweeb chain?). Comic book collectors, Trekkers, gamers, cosplayers, Harry Potter or Twilight fans, baseball stat fanatics, record collectors, scrapboookers, whatever... geeks is geeks is geeks. As Athena Voltaire & Ursula Wilde creator Steve Bryant said in a brilliant post over on the Comic Geek Speak podcast forum,
Everyone's a geek about something. I've worked in the roleplaying game industry and the comics industry (and been to conventions) and have worked at a gun magazine (and been to the NRA show). I've been to sports fan appreciation shows and Beatlefest. My ex-wife was an avid quilter, so I've been to many a quilting/sewing show...
...the only thing that changes is the T-shirts.
And lastly, my fellow geeks of all stripes... you are familiar with some of the stuff we like, right? I mean, you've taken a really good, hard look at your objets de fandom of preference and really considered it on the intellectual level, right? Even when compared to the vampires of Twilight, sparkly like My Little Ponies though they may be, we haven't got a leg to stand on where most of this stuff is concerned, folks.
(Also, if you're the sort of person who is actually afraid of something that promises to bring - EEK! - girls to Comic-Con, then you're also probably the sort of person that none of these girls would ever have any interest in talking to, anyway. Nor would they ever dream of disrupting the special bond between you and your Megan Fox poster. So you've nothing to worry about.)