This basically confirms the bluepost from the forum that there's no news coming before Blizzcon.
And this just makes me believe more that the WoW news are more than just 8.3 or 9.0. I think there will be a sub model / another huge change for WoW. If it's just the generic expansion announcement and 8.3 exists it makes no sense to delay its announcement so much.
If we think about it: what huge / massives changes could be made to WoW or it's business / expansion model?