The setting I'd most like to see ported over from Magic to D&D is the setting for the Ravnica block of Magic. Now, I don't play Magic, but I have friends who do, and they told me enough about this setting to get me really jazzed about it. There's this whole planet that is one big city, and it's being fought over by several different guilds. I love how the different elements play into the setting, and it seems like it's custom-built for urban adventuring, political intrigue, and crazy fantastic magic.
There's a bit about
Ravnica on the Wikipedia. I've often thought about setting my next D&D game there (just for fun) and it seems like there's a lot of neat stuff to be done with it.