Batman-News have posted an image from The Dark Knight Rises set. It appears to contain similar armor to the Batmobile in an unfamiliar array. The rig underneath could either be part of it or supporting it. Batman-News are suggesting that it is the Batwing. It could also be a detached part of another vehicle or the armour raised up for access to the engine.
I suggest that all may not be as it seems. Let's wait for another image before we start getting excited that the Batwing is confirmed.
Any other thoughts on what it could be?
Source: Batman News
Update: New photo from DailyBlam shows that the vehicle is indeed separate from the rig.
Definitely a flying vehicle. Looks like an attack helicopter crossed with a stealth fighter. Check it out in this video.