Yep, new BG/pvp stuffs are "siege warfare and destructible buildings" in that photo, along with a new BG. Looks like that leaked QA was word for word correct. I'd be very surprised if they didn't have more information ready by now, though... the vague handwaving over "unlocking" the deathknight will probably cause a small riot if there isn't more to know.
Here's the sidebar text:
Some of the highlights you will learn more about at BlizzCon:- The dark, necromantic Death Knight - the first new character class added to World of Warcraft since launch.
- Northrend, the harsh, icy continent where the Lich King holds sway - complete with new zones, quests, items, and monsters.
- New level cap of 80 - including access to mighty new powers and talents.
- New Battlegrounds: featuring siege warfare and destructible buildings.
- Expanding character customization options, including new hairstyles and dances, the ability to change the hairstyles of existing characters, and new skin color variants.