Without ever having attended one, I can guarantee you OP that every employee is briefed in a meeting before Blizzcon to smile at every question, and never shoot anything down directly, instead be vague. "Is there going to be a D4?!", *employee smiles*, "What, are you trying to get my fired?!" doesn't actually mean anything, at all.
If they weren't even ready to *announce* anything, and in the same breath tell us the Necro will be at least 8 months out, we AREN'T getting anything new, expansion or otherwise, for YEARS. We'll be lucky if they even talk about anything at the NEXT Blizzcon.
Stop hyping yourself, and just play games you enjoy, it'l make everything a lot more fun.