Does it really matter? Beyond the guild of over-zealous parents who think computer games are the source of all evil, I imagine the majority of gamers wouldn't mind a porn star being there. Video games, whether an art form or not, can appeal to all people so I don't think anyone should neglected from a 'launch party'. In all fairness, I'm not a fan of MW. But I've played it, enjoyed it and I've watched a lot of friends playing it. Even if she went there naked, I doubt many heads would turn to look at her if there was a demo to play instead.
"Oh look, a sexually attractive naked chick. She won't sleep with my 300lb ass. But the ones on my computer screen probably wouldn't object to me masturbating in front of them after a marathon of Modern Warfare 3. Maybe on my way out, I could 'accidentally' bump into her bumps, but that would be of no interest once I tell my friends I was at the launch part of mother loving MODERN WARFARE 3!!!!"
Sorry, I am cynical. If you're there for a lauch party, would you really care if a porn star was there or not? If I was invited to a lauch party for a game I enjoyed, I would just be impressed if a 'celebrity' showed up because they enjoyed the game. I'd like them more as a person, but if they were a crap actor or someone I generally avoided, I wouldn't think any differently of their abilities afterwards.