Well, both WoW and D3 are loot based games -- at their hearts, you kill monsters for their loot in both. Diablo III's Loot 2.0 is an amazing system for itself -- it's fun and exciting when the loot you get from monsters ends up being awesome. But for WoW I think a system this personally rewarding would be insane. World of Warcraft is not set up for you to have some of the coolest, best items you'll ever see just drop from random trash, because WoW isn't a game designed around the idea of constantly going on reaping trash stomping dungeon crawls. The social aspect of WoW, with communal play of small 3, 5 and larger group content isn't the same as D3 and its multiplayer. If anything, Warlords' item squish is already a cautionary tale of the kind of excess that Diablo III not only rewards, but exults in. Nothing helps drive the lesson home that these are different games like their different approaches to loot.
That said, WoW can learn something from D3 in terms of the way loot works.