Nethaera has confirmed that there will be no new battlegrounds revealed prior to the release of Wrath of the Lich King, much to the chagrin of PvP'ers everywhere. Although players have previously expressed interest in having more choice, Blizzard has voiced concern about the effects that a fifth choice might have on queues. Hopefully they have some tricks up their sleeves for combating this when the highly anticipated new battleground arrives via the expansion.
Although this is a bit disappointing, it is hardly unexpected, and there are so many upcoming positive changes that it's hard to be a sad panda for long. Currently, the devs are focused on improving Alterac Valley for patch 2.3 and creating new content for WotLK, which will include an outdoor PvP zone, Lake Wintergrasp. Following in the wake of Halaa's undeniable success, this zone will boast siege warfare, and many other innovations in world PvP.
As for what the new battleground will be like? I'd still love to see an Aldor vs. Scryers battleground; and as much as we all love to see new content drop, we can at least try to satiate ourselves knowing that what we will be getting will continue to advance PvP as we know it. Now; a little less sad panda face please!