I've read some threads about this topic wether Diablo 3 is going to released, I really doubt even if it is going to be released it won't be close to Diablo 1 or 2.
First off, Blizzard North created the Diablo Universe, and no Blizzard North is not Blizzard, its the branch of Blizzard for Diablo. And if you don't know already, Blizzard North was disbanded in 2004, the Diablo makers are currently divided into 7 different companies.
Secondly, if Blizzard decides to create Diablo 3, they either:
A) Hire back the original employees of Blizzard North
or
B) Create a whole different team and hand the reigns of Diablo to them
Honestly, after the big conflict between Blizzard North and Blizzard and the disband of Blizzard North, I think that they would be very agitated for Blizzard to hire them back again.
As for the 'newbie team' Blizzard is hiring, I think we can all agree that NO ONE can match up to the designing skills of the original creators
So if Diablo 3 were to be made, and not from Blizzard North, it won't be as great as Diablo 1 and 2