Blizzard released only two games on consoles - Starcraft 64 and Diablo for the PS
Actually they've done a lot of console games: Blackthorne, Rock 'n' Roll Racing, Death & Return of Superman, Justice League Task Force & Lost Vikings 1 & 2, some of which were console only. They also did Warcraft 1 & 2 for PSX. Of course this was when Blizzard were a different company, from what I understand not one person working on Diablo 3 has worked on the previous two.
They always said that they wanted to make games for consoles but time constraints prevent them. Would be nice if they stepped out of their comfort zone and did something new for a change that wasn't a sequel or spin off, I know they've got a MMO called Titan but that just sounds like WoW in space.
I bet they have a good contract with Activision, something that states "you can't port our shit unless we say so" because otherwise Activision would have milked their franchises dry.