Apparently Cataclysm will be available on release day as a download, according to the new banners on the 4.0 wow launcher.
"Activate Your Background Downloader NOW and Be Ready for Day One!"
MMO also has a thread regarding this:
http://www.mmo-champion.com/threads/763894-Cataclysm-Digital-Download
i cant even begin to fathom the bandwidth required to service 13 million people downloading 6 gigs. they must've contracted out to every CDN on the planet.
edit: thanks, google
6 gigabytes x 13 million = 74.3865967 petabytes
well consider only 1/2 will buy in first 24 hours, of that half, at least 1/4 i would say, will buy special edition and can't download.
another % of the 6 million buying won't be able to download due to limited internet so i would say, that digital download in first 24 hours, will likely be under 2-3 million
Totally guestimating off the top of my head, but will be interesting to see
You're also forgetting the *leagues* of people that have multiple accounts.
2 accounts on same computer? Only need one copy. 3? 4? still one copy. =)
If you're not going the digital download route, and you still want to get everything installed on your computer so you don't have to deal with it launch night, you can download the data early.
This article explains what to do to start the ~700MB download
wow.joystiq.com/2010/10/29/want-to-preload-cataclysm-without-pre-ordering-heres-how/