16:9 screen? Eww no thanks
Also ARM doesn't have any 64 bit CPU designs available yet.
But anyways, pretty much the one thing I want from iPad 3 is a retina display. I feel like the retina display has to be coming, otherwise iPad 3 would be the worst incremental upgrade ever. Mainly because the iPad 2 is already the fastest iOS device available, a speed bump would be incredibly lame.
Other than that it would be cool if the Wifi version also got a GPS chip built in. They probably don't do it because people would complain of slow satellite lock times (compared to their smartphone with cell tower assistance.) Better speakers would also be a nice addition.