No offense, but that wouldn't be a very difficult thing to do. The current 256MB is a joke on a 10" device, when some smartphones have twice as much.
At least one camera is inevitable now and the screen will have to move towards what you find on the iPhone. Also, when the iPad was launched, multitasking was not on the agenda, but probably due to public and media/press pressure, Apple had to bring that to the iPad soon after. But the hardware is not really there to support web browsing with several tabs and having other applications running in the background.
I think that the RAM will be the biggest issue. If Apple will release the iPad with 512MB, the next generation iPhone will again have more than the iPad. If Apple wants to do it properly, that will mean that developers will have to choose between developing an app for the old or the new iPad, that's how much difference another 512MB RAM would make.