That Tolarian Community College Professor actually mentions the possibility of a Zandikar themed D&D book coming out when Zendikar Rising does.
He might be reading this forum: then, he probably has sources in the playtested community, and WotC can't keep a lid on things forever.
What art books are already out? This thread is making me want to see and maybe get somez
Theros would probably be at the top of my list of MtG settings, along with Amonket, preferably a region they didn't destroy. I like the Kor race from Zandikar, and what look like it's subclasses, but the setting itself isn't that interesting to me besides from Eldrazi who aren't there anymore.
And of course Ravnica, but they already did that one.
Looking again at the Planeshift article, if you don't include races, subclasses, and Monsters, just world lore, you could likely fit most of them into say 10 to 15 pages which would leave space for new details. A lot of the Planeshifts are taken up by space for art, over 50% or more on the average page is art.