I disagree, there is a point where you can be too light, I've already heard an apple diehard say his ipad2 is too light.

What would be more likely is keeping the weight the same but increasing battery life, imho thats how they made the ipad2 lighter than the ipad1, think about it, smaller manufacturing process in the CPU and other internal components than the ipad1 had in the ipad2, therefor less voltage required, they hit the same life with less power so they can use a smaller battery and get the same results in a "thinner, lighter more powerful ipad".
If the screen and other "new" features in the ipad3 can do it with the same or less power they can either reduce battery size again and make it lighter/thinner again, or they could keep the same battery and then just keep it the same weight as the ipad2, imagine how long it'd take the "other" tablet manu's to respond to something faster than the ipad2 with a higher res screen, iphone4s spec camera's (ie 8mp but with improved optics etc) but with an extra few hours bolted onto the battery life...

For there normal price point of £349 or whatever the 16Gb iPad Wifi model is...