http://us.battle.net/wow/en/forum/topic/20743924233#11
Seems like new biggest number that WoW can hold is 9 quadrillion +
I wonder if they'll decide for another stat squish in the future to keep numbers low or go with it like diablo style once we reach a point where every ability and autoattack does milions so we'll see things like 34 000 M etc.
I guess if they decide for no stat squish they can please both sides that are for and against it by adding M, B , T etc letters to the numbers or add option for that like in Diablo.