I hope this won't turn out to be like that time where they had a "big" announcement and it turned out to be that Hearthstone card game
It could be the D3 expansion... But what about the last wow expansion? didn't they say there is going to be another one after MOP? It could also be just information about a big patch like 2.0 for D3 or something.
"Patch 2.0" would actually be the xpac... the leading version number is always 1 + xpac number.
My guess is that they will release loot 2.0 at the same time as the xpac, affecting both vanilla and upgrades. This is what they did with the last sc2 xpac.