We'll have to wait till it comes out to see how Apple promotes it.
There are several possible uses for a larger iPad.
For trade shows and point-of-sales applications, education or anywhere more than one person looks at the screen at the same time a larger screen would be helpful. This doesn't need faster electronics or more pixels.
For remote access of a desktop computer more real estate is helpful. There are enough pixels, the iPad has more pixels than most desktop/laptop computers. The problem is space. The digitizer on the screen is too coarse for you to easily select features on the screen. You have to zoom in to get them reliably. More real estate and a more precise digitizer would fix that.
Similarly, I can see all sorts of augmented reality applications that would benefit from more real estate. A better camera or multiple cameras or better located camera might help. How cool would it be to view a neighborhood and see where all the buried pipes and cables are, where the fence lines are and such as you move the iPad around?
For engineering or graphic design something with more horsepower might suit some, but not all, applications.
I'm not an artist but I can imagine that a larger canvas would be appreciated by those who "paint" on an iPad.
This is just off the top of my head. I'm sure the Apple guys will think about this a little harder. Anyway, it would seem that many applications would benefit from just getting a larger screen and maybe a better digitizer. Some would want more speed but probably a small minority.
