From Cringley's May 5 column (link mine):
And 10.4 gives us a peek at another evolution of iTunes, which is the inevitable expansion of the system to carry additional audio file formats. Looking at the unused iTunes icons that shipped with your new version of 10.4, you'll notice icons for currently-not-supported ogg vorbis and Windows Media Audio (wma), as well as several others including a variety of video formats, too.With this new information we can make a pretty good guess about the evolution of both iTunes and iPod. When Apple feels that the success of iTunes is absolutely assured, which will be shortly, they'll address the user complaint that iPod only supports AAC and MP3 audio by adding these additional formats, leading to increased iPod sales. And at the same time, the video icons strongly suggest that Apple will also have a video iPod this year.