updated 10:03 am EST, Tue November 19, 2013
May be supported by recent rumors
A "first-tier display supplier" is working on 12.9-inch Retina displays for an iPad due to launch in early 2014, claims the Korea Times. The publication cites an official at one of Apple's Korean suppliers. Based on Apple's known partners in the region, that implies either LG Display or Samsung, either of whom would be large enough to support an iPad launch.
The supplier source mentions little else except that the new iPad model will have improved picture quality comparable to "ultra high-definition" displays. That could imply something equivalent to 4K resolution, higher even than the resolution on the iPad Air or mini.
A number of rumors have hinted at production of a bigger iPad. Earlier in November, one suggested that Foxconn was testing production of a larger iPad for spring 2014. Back in July, the Wall Street Journal noted that Apple had been experimenting with both a 13-inch iPad and an iPhone with a larger display.
Given the renaming of the 9.7-inch iPad as the iPad Air, Apple may be preparing to christen a 13-inch "iPad Pro," mirroring its Mac lineup. What other features a Pro tablet might have are uncertain, but Apple would presumably want to make it more practical for work purposes, for instance by adding a USB port or more RAM.