Personally, I don't think I would need a larger iPad...since side-by-side apps are not a possibility (yet) without a jailbreak. A larger iPad would probably maintain the same resolution of the retina iPad at 2048x1536. Side-by-side app functionalilty is a must for a larger, more expensive iPad size to be successful in my opinion.
The iPad Pro could be focused toward kiosk functionality and other business functionality, this could certainly be successful. The size of the market interested would be somewhat in question though.