This is going to be a really lame upgrade.
I agree in part with you. I think the patented incremental Apple upgrades (sligthly thinner, sligthly faster, with a sligthly better camera) are less significant on the iPad than on the iPhone since the former has no contract incentiving people to replace it every two years.
I have no reason to upgrade from my iPad 3, for example. Sure, the iPad 5 will be smaller, but the size and weight of the iPad 3 don't bother me. I would like to update if:
The new iPad had some new (useful) feature, allowing us to do something (interesting) that today is not viable. A flash would fit here - today it's not viable to take pictures in the dark.
The new iPad had something improved so much that it would feel almost like a new feature. True multitasking, for example - I would love to be able to open GoodReader and Pages at the same time, so I could write a document while consulting a PDF.
There were a new and important app exclusive to the new iPad. Office for the iPad would make my life significantly easier if implemented well, for example; if it were exclusive to the new iPad, I would upgrade without a doubt.
The new iPad had a bigger screen. Something sligthly bigger, with the device at the size of a paper notebook, with a bigger keyboard and at the same time a smaller percentage of the screen taken by the keyboard, would be great for typing on the go.
But, to say the truth, only the first and the fourth points have anything to do with the hardware, the other two are a matter of software. And I doubt very much iOS 7 has any surprise in store for the announcement of the new iPads.