I like killing monsters for loot, the problem is that loot rarely drops - to a point where I can't get myself to care about continuing; and nah I'm not interesting in the AH. Now I could endlessly farm the same content for hours and I'd imagine eventually my paragon level would ensure some good drops...but the game isn't interesting enough to make me WANT to do that. Not hating on it, as I said I had a shit ton of fun...I just feel like I've already accomplished enough in the game. Didn't kill Diablo on inferno but don't really care to, which goes back to the whole "grinding boring monsters for barely any loot" thing.
As it stands, I would lean against buying the expansion unless the game sees to big changes, but if Triumph, Viz, and other e-bros are playing it again that would certainly compel me to jump back in.