I love what they're doing with the whole Duel Decks concept...
They start off with the Elves vs. Goblins (Green vs. Red), move onto Jace vs. Chandra (Classic Blue vs. Red) and then onto Divine vs. Demonic which is blatantly White vs. Black. At this rate we'll get a whole host of worthy matchups.
An idea that springs to my mind is: Slivers vs. Saprolings...

Me and my silly mind...