There's a little bit more scattered out there about it, but not much as far as I have seen.
Blizzard North began working on D3 in 2000, lots of the BN crew left in 2003, and the project continued at BN until mid-2005 when BN ceased to be and D3 was moved into Irvine. http://kotaku.com/116290/diablo-3-trashed
Here's Mr. Schaefer talking a little bit more about the D3 MMO, the first time it was revealed as such I think. (He also mentions that they declined to make more D2 expansions on principle, wanting to modernize the game, despite knowing they would sell like hotcakes. Kudos, Blizzard North.) http://www.diablopodcast.com/the-diablo-podcast-episode-one/
In that podcast interview, Max said at the time he was working there the Heaven area shown in these screenshots of the BN version didn't exist. Possibly gives some credence to the Hartgraves and Gaming Steve leaks, since I believe the SS's didn't leak until 2010? http://diablo.incgamers.com/gallery/showgallery.php/cat/600
If that new Max Schaefer interview is accurate, he seems to be saying D3 was still an MMO up until 2005 when it got moved into Irvine and became what we are playing today.
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I think the release of WoW on November 2004 was the motivating force. After many of the original D2 team left, all their energies went into WoW development. shuffling of talent and whatnot. m2c anyhow.