BlizzCon 2008 has just been officially announced:
Blizzard Entertainment - Press Release

October 10-11 in Anaheim, CA.

I'm going to guess that this will be the announcement of their next MMO, amongst other things.

Let's hope it will be Diablo 3 and I can prepare to be abandoned by friends and family when I become hopelessly addicted to it.

Not MMO, but DiabloIII - next generation hack'n'slash.

What we really are missing in todays gaming is exactly that. It could possibly be a guild wars type game too, which really is only an "online in game lobby".

Diablo 2 is kind of like a gimp WoW when you really think about it.

And the first time I played WoW in beta I thought to myself, "This is basically a much more polished version of D2, with Warcraft characters".

I can't think of much of a reason why you wouldn't want to make D3 a MMO, just so it can be a much deeper game.