Don't hold your breath. Blizzard is busy working on WarCraft III and World of WarCraft. Also, Blizzard is known to take their sweet time working on their games (which is perfectly ok because their games rule!). And they hardly ever ship anything on time. Just look at how much Diablo II was delayed...and then the expansion.
For now, just keep playing Diablo II, and do like I did and beat the game using all the characters, and then build them up to massive levels to wreak havoc on battle.net =)