I didn’t notice that AVFoundation was in Snow Leopard, but it was there in iOS.
It seems to me that AVFoundation is going to replace QTKit/QuickTime.
Here are some posts on the issue.
Steve Jobs said that Mac OS X Lion is to bring advancement in iOS to Mac OS X. It may not be only the UI, but frameworks.
ADDED : From iOS ?.? doc: The AV Foundation framework provides Objective-C interface… in your Mac OS X application.
That is why I thought it was in Snow Leopard. However, I searched it again, and it has never been in Mac OS X SDK.