Apple already "supports" codecs in Safari if you install them (e.g. you can do this now with Theora via the XipQT plugin) and there's a WebM plugin due in a couple of weeks from Google apparently, and I'd guess a newer version of Perian would also work once upstream FFMPEG accepts the patches.

The reason they didn't need to announce this support (apart from the fact that they might not want to give any attention to what they view as a competitor) is because, unlike Microsoft, they hadn't just announced the week before that they would blacklist all other installed codecs and only use H.264.