most people that will buy it have already pre-ordered their copies. Believe me, its gonna he like hell unleashed when it comes out. (I expect everyone that has the game to buy a copy of that - i pre-ordered it 4 months ago :P)
They'd wait a little while for things to calm down before the announcement anyway. about Februar/March would be my guess for us to know which game its gonna be.
it wont take much longer. We'll get the new talent lines earlier with a patch, together with the brand new honor system. It will only take a few weeks. I wouldnt expect the news for Diablo 3 before tbc has sold less than 4-5 million copies anyway ^^
They'd wait a little while for things to calm down before the announcement anyway. about Februar/March would be my guess for us to know which game its gonna be.