When could Blizzard make new announcements?

Is there any upcoming event or scheduled dates of anything, in which Blizzard could possibly use the attention to announce the zerg units, or any new feature in the game? Since the game is probably set to be released next year, perhaps they wouldn't let leak the entire information about units this soon (whenever you read this, we're in early August now). And we have already the entire tech trees for Terrans and Protoss. Does this means we gonna have to wait (a lot at least)?

 

liepzig is the only other convention i can think of for this year, although thats to soon for another big announcement

 

September 8th? That's not too soon, considering they might just show a little bit of zerg mechanics and not all zerg units.