Expansion focuses on Horde vs Alliance conflict (what exactly this means for PVP in the long run is uncertain).
Chris Metzen touched on this in the reveal for Mists during the opening ceremony saying that one of the central themes of Mists was going to be renewed Horde vs Alliance conflict in the absence of an external threat. How this will affect the importance of PVP in the expansion remains to be seen, however three new battlegrounds would be the most ever included in an expansion so that is a start.
Three new POTENTIAL battlegrounds based on game types that are new to WoW.
Cory Stockton responded to my twitter question about these BG's during an interview on the Direct TV stream saying that they are hoping to have all three new BG's in at release, but it remains to be seen if they will meet that goal. The question also asked if they would be 10v10 or 15v15 but he didn't answer that part of the question (probably just forgot) but we know that at least SDM will be 15v15. It does seem that STV Diamond Mine and Valley of Power are currently the more fleshed out concepts as we didn't get a concept map or any real detail on Azshara Crater. I personally wouldn't be surprised to see one or two of these maps pushed back to a post-launch patch, but I live in hope!
Stranglethorn Diamond Mine (SDM)
Here is an enlarged version of the SDM concept map, I also re-did all the text to make it more easily readable.
Here is the SDM concept art.
SDM looks like a very interesting map although I am a bit concerned about a few things:
Continues in next post.