For all the people that don't know, heres the basis of Blizzard, and how things work.
Blizzard originally had one main core part. It was responsible for WC and before. Their graphics division, Blizzard North, then was broken off, and told to produce a goundbreaking game. This is where Diablo came from. SC was made from a completely different crew as Diablo, or Diablo II. The crew never worked on eachothers projects (with the exception of the graphics crew, the original Blizzard North)
I believe now that WoW has grown to it's peak ( to an extent ) they have branched off a third part of the company, to deal exclusivly with WoW, and its expansions. I'm not 100% on this info yet, but it's the most logical thing to do.
Many of the top producers of the Diablo/SC and WC franchise were "tired" of Blizzard ( to say the least ) and left to make their own their own companies,
www.arena.net and
www.flagshipstudios.com
Since then, Blizzard hasn't worked on anything
major that wasn't 85%+ done when the crew left. This is why you see the job requests for all the positions out there now. They're starting up on a different franchise, and they need developers/other lackies to do the work.
Sources: www.blizzard.com // http://www.arena.net/news/index.html // http://www.flagshipstudios.com/index.htm // other pages on the net, fileplanet/gamespy, that kinda shit...you know