I hate to interrupt the Metal Gear like cicle jerk, but why is Blizzard so conservative? Both SC2 and Diablo 3 seem just like their predecessors, only with new assets.
I mean from a biz-dev perspective I understand that innovation is a bad word, but I'd figure with all Blizzard's money, they be emboldened to take risks. I guess all their current employees grew up playing Starcraft and Diablo, so maybe it's the rank and file's dream to get to remake these games 
First of all, we only know a handful of details so far so that's not a fair assumption to make at this point.
Second, as a hardcore D2 fanboy that played the game for hundreds (probably thousands) of hours, an updated D2 is exactly what I wanted. I bet a lot of other hardcores would agree with me.
Third, from what we do know, there are some significant changes. The environment interactions and physics is a huge change. D2's environments were like bitmaps.
They're also changing the loot system, the health system, vastly improving B.net, making quests much more dynamic, etc.
Lots of good details in this chat transcript from dii.net:
http://www.diabloii.net/n/668039/diablo-qampa-diinet-transcript