Same screen size. Higher resolution. I think that a mere doubling of the pixel density would be sufficient.
RAM memory at least on par with the iphone 4. It just feels "wrong" to have less.
Sure enough I too want less weight, cameras yadda yadda, but they are not necessery. I also wouldn't go for then, unless the first two conditions were satisfied.
And now for the hard one.
An additional wacom like digitizer under the screen and a stylus.
Onoes D: Blasphemy I know. But look.
I get it why not on the iphone. I agree. However the iPad is a completely different device.
It is no secret that a lot of Apple's fans are "artists" and Photoshop users. There is then a class of devices, called graphics tablets, which Apple could so easily hit. And hit hard, if only it did that thing. While make-ing the ipad a true moleskin sketchbook / electronic canvas replacement.
There are a lot of screen-less graphics tablets, which had always been a bit awkward to use, because you have to draw in one place, and look at another (I never got the hang of them). There are also a very select few which combine a screen and graphics tablet (the Cintiqs) which are pretty much the dream of any photoshop artists, if it weren't for their outrageous prices. Ie:
http://www.wacom.eu/index2.asp?lang=en&pid=96
That's right. A stand alone, wired, device that does one single thing. Which does nothing more than mirror a screen and relay back the position & pressure data of a pen, actually costs more than an ipad!
And that's the "small & cheap" one. You don't want to know about the other one.
If Apple put such a sensor (one which at no point requires the capacitative screen to be taken out. You would still have multitouch and a glass surface) it would literally decimate wacom, and it would go a long way towards justifying the ipad's price and as a special category of device. Presumably it would also make it more useful when it comes to "taking lecture notes" and such, you often hear people complain about.
Ideally the ipad would be differentiated between "stylus having" and "not so", rather than the current "sim slot having" and "not". And I for one, wouldn't mind paying £100-£200 extra just for that.