Think iPhone 4, but bigger.
And to be honest. I think Apple will make us wait a while for the iPad 2.
I'm not getting what the obsession here is with "Retina Display". I think it's a little confusing to people what it actually is. It's basically a step towards Resolution Independence in the OS, and the way they manufacture the screen.
The first of those two things you can expect in iOS, as they are ultimately going to unify the iPad, iPhone and iPod OS.
I don't see the second coming any time soon... 300 odd pixels per inch on an iPad sized display?
They'd need a whole new GPU in the SoC before they even considered that.