A few days ago I listed the rumor that we'll see a 4K "iPad Pro" as one of the craziest rumors of 2013. Yet the rumor keeps popping up. A 4K display would have twice the resolution of today's retina iPad. To my mind, it's not credible, given the difficulty and expense. Plus, it's not clear to me whether the unaided eye would even be able to see the difference. You can read about the latest rumor on Forbes, which cites as it sources the Chinese language website Pad News as well as Foxconn, the Chinese company that manufactures many of Apple's devices. According to one rumor, Apple already has a prototype ready of a retina iPad Pro and is now working on developing a 4K version of the iPad Pro. By way of comparison, the retina display of the iPad Air has a resolution of 2048 x 1536, while an iPad with a 4K display would have a resolution of 4096 x 3072.
So why 4K? The Forbes article says it would be useful for watching ultra high-definition movies and for "big data" visualization. Also, given that video is moving toward a 4K standard, it would be useful for Apple to offer a portable device to complement Apple's new Mac Pro that could shoot and edit video in native 4K resolution.
Still, a 4K iPad is a stretch (so to speak), but I'm guessing the rumored iPad Pro with a 12.9-inch display is much more likely. An interesting article on Computerworld talks about the iPad Pro being perfect for the education market and suggests this is what Apple may have in mind. The article says that the big challenge Apple and Microsoft face today is transitioning to the Post-PC world. Educators will increasingly be replacing their desktop computers with tablets. But the article says that today's 9.7-inch iPad isn't the optimal size for the classroom. The iPad Pro would be a perfect Post-PC solution in terms of size and relative cost.
The article discusses other options available, such as Chromebooks, that might be options for the classroom, but concludes that none are optimal and that a 12.9-inch iPad would fill the bill.