In the long run, this might be a mixed-blessing for Apple. Seeing as how they are just now entering the games market and are riding the crest of their ultra-trendy wave, they can probably just invest in social media, free to play, or other "lite" versions of games rather than the more capital intensive "AAA" version that Bungie represents.
Both companies need to recognize who their core demographic is. With Apple, it's more image-savvy people (women) who don't care for serious gaming. Windows, on the other hand, has more of a "core gamer" demographic as its customer base. Microsoft seems to be recognizing this trend (belatedly, again) with their oft-revamped Games for Windows program. If Apple is truly the visionary company they often prove themselves to be, they should see the writing on the wall and invest in more casual, trendy-friendly gaming. I personally think they are on the right track by concentrating on providing the best, sleekest, most hip platform on which games can be played, and letting others worry about developing the content itself. That being said, they can probably afford to invest a bit in the content-generation business as well.