The A4 processor in the current model will be replaced with the new dual-core A5 and the SGX543 GPU which should have about 4X the current graphics processing power, lending some credence to the next rumor.
Retina display? While the new GPU could theoretically handle 4X the pixels, or twice the resolution in both directions as the current model, I’m skeptical about this actually materializing. Apple could produce said panel and the new processor could push the needed graphics, but I don’t think they could hit the needed price points with an LCD panel of this quality. I think a bump in resolution is possible, but 2048x1532 is very unlikely.
The new slate will likely have both rear and front facing cameras to facilitate taking snapshots and video conferencing respectively. Recent leaks have indicated that the rear facing camera will be a measly 1MP, while the front camera will be VGA (640x480). VGA front facing cameras are pretty standard fare on current generation smartphones, so I expect this to be accurate. I would, however, be surprised if the rear camera was only 1MP. I think it more likely that the folks in Cupertino use the same camera in the current iPhone4 at 5MP, or possibly a cheaper 3MP version. It is also possible that the leaked information was only half accurate and the 1MP camera is actually the front facing one.
A new sensor may be in store for the new iPad as well. This could be used for some fancy new locking/unlocking features.
Apple doesn’t usually like to offer anything in the way of user upgradable storage, but this apparent leak seems to keep popping up. I think the SD card slot has a good chance of making it into the new units, but being able to use it as additional storage is a long shot. Expect it to be limited to certain uses related to viewing digital pictures from your point-and-shoot or digital SLR camera.
To simplify manufacturing, the next generation slate will tout a dual network capable GSM/CDMA radio chipset from Qualcomm. This falls in line with the recent iPhone4 on Verizon announcement and would let Apple sell the same unit for both carriers. The iPhone5 will probably follow suit.