In Diablo 3, there technically is PvP... but not really. In Diablo 2, PvP is the end-game. It's pretty nice, and with a bit of fine-tuning, updating, and with an HD update, it would be sick.
Then again, D2 > D3 on most things anyways.
Grind-based games are in my past now anyway, so D4 probably won't appeal to me.
Hope they do a remake of Diablo 2 and make everything in D3 non-canon.