Blizzard announced that upon launch on the 13th of November, WoW will only be available in DVD format. This is one more indicator that we'll soon be seeing less and less CDs around as we're slowly drawing close to dumping it like cassette tapes.
Although DVDs are a more practical option compared to 5-6 CDs, they will eventually push CDs out of the audio market, too, as 24-bit, 192 KHz quality is something that no CD can contain. And it really sounds impressive, take it from an audiophile.
This is basically how the industry grows based on the demand. First, you need CDs for audio, and then you all but dump them for MP3 formats. Then, DVD audio comes along with its far superior quality, and suddenly the old MP3s don't sound as good, so you need better ones that will, of course be bigger.
Then in turn, network operators smile, buy more servers, push the bandwidth to the sky and happily pick your cash while you download new compressed albums. Except this time, “compressed” probably means 2GB or so.