I hope that the display is closer to 11.9". 12.9" seems pretty hefty for a tablet.
I'd love to be able to do design and photo editing work on one of these someday. iOS needs better file management, peripheral support (think app store for USB device drivers) and improved multitasking capabilities before it could be used by professionals. I think things are slowly moving that way, but it will be a while before many professionals can take it seriously. There also need to be some better professional apps for iOS. I bet Apple releases at least Aperture and Logic for iPad Pro. Final Cut X is really pushing it, and it would have to be a pretty powerful device with a much more advanced iOS. I can't see anyone using that right now. I know Adobe is working on Lightroom for iPad. RAW editing apps would be a great start and good use.
Does anyone think it's possible that Apple could create and edge-to-edge display? Maybe with just a tiny bezel to reduce overall size? What I'm thinking is that an iPad Pro would be targeted at creatives and would have a pressure sensitive screen. Touch capacitance combined with pressure sensitivity could, in theory, combine to create better edge touch rejection. It could much more clearly recognize someone holding the device vs. trying to tap on something. I'm just not sure if they can ever get rid of the top and bottom with the FaceTime camera and home button. But a minimal bezel iPad Pro 11.9" wouldn't be significantly bigger than an iPad Air.