Well its coming at some point, we just do not know when but the tech blogs and news sites are running rampant with rumors. Most are pointing to a late february (not likely at this point) to March release date. My guess after seeing how these things play out and are always a bit behind is March/April.
Thicker than iPad 2
Significantly improved battery life
Also, iPad 2 price will drop and may continue to be sold
Well these are all rumors so take them with a grain of salt but be ready in the next 2 months to see iPad 3.
Here is a good site that explains the recent rumors: http://mashable.com/2012/02/01/ipad-3-details-2/