Then there's a newbie question for anyone: Do Duel Decks ever feature brand new cards...? For example, I shouldn't hold my breath for any new flip cards should I..? (specifically werewolves) Nor would they include an new version of Tibalt unless he is popping up in a set in the next couple months...?
Duel decks have never before included brand new cards. The closest we've come to that before are "preview cards", which we got in the recent Izzet vs Golgari, and we also got in FtV sets for a while. So, the only way we could expect to see any new cards is if they're cards that are about to come out in Dragon's Maze. That in mind, we won't see any new flip cards. They aren't a theme of the block, and there aren't any other sets close enough on the horizon. It's also highly unlikely that we'll see a new Tibalt in DGM, since currently Ral Zarek has been confirmed to be in the set (though in all fairness, not confirmed to necessarily appear as a Planeswalker card. He could show up as a legendary crreature, allowing Tibalt some space to move in). I wouldn't hold my breath.
EDIT: Egad, I've been snaked.
Favorite set: Arabian Nights Favorite planeswalker: Taysir, the One Made of Five Favorite book cycle: Ice Age Favorite creature type(s): Elephant (W), Minotaur (R), Shade (B), Spider (G), Cephalid (U) Myr (Artifact) Standard: Gruul Control Modern: American Human Tempo; Zombie Tribal EDH: Aboshan, Cephalid Emperor Cube: The Moons of Mirrodin
There's a Wizards article somewhere that talks about preview cards in duel decks. They aren't likely to have them for Planeswalker vs. Planeswalker duel decks because those decks are supposed to be about the Planeswalkers. Wizards was unhappy with the Elspeth vs. Tezzeret reception because all anybody wanted to talk about was Contagion Clasp . It's one of the reasons why they shifted the Planeswalker duel decks to be released in March, and the Faction duel decks to be released in September.
Which of course means IvG is likely all we'll get for Ravnica Duel Decks, at least until the next Ravnica block. I could be wrong, and we could see one or two more, but that's the limit I'd expect. And right, I forgot about Contagion Clasp.
If StarCity is any indication, he's worth the entire MSRP of Sorin vs. Tibalt alone.
He's been dropping quite a bit though, and this will only make him fall in price further. Which I'm A-Okay with, because I want myself a few, and the DD art is great looking.
I'm quite fond of them both, really. I'm glad Tibalt's will be wicked cheap, because I definitely plan to pick up a couple.
Favorite set: Arabian Nights Favorite planeswalker: Taysir, the One Made of Five Favorite book cycle: Ice Age Favorite creature type(s): Elephant (W), Minotaur (R), Shade (B), Spider (G), Cephalid (U) Myr (Artifact) Standard: Gruul Control Modern: American Human Tempo; Zombie Tribal EDH: Aboshan, Cephalid Emperor Cube: The Moons of Mirrodin
Considering that it's a different version and that the duel decks do not make the regular and booster pack foil versions more available, it's not going to impact the price that much. This version however will likely have a lower cost as is usual for prepackaged foils. Incidentally, Lord of Innistrad is the highest value Planeswalker card they've featured in a Duel Decks since Elspth, Knight-Errant which at the time of this post is the most valuable planeswalker card they've ever featured in a duel decks to date.
Proliferate w/ 
Elves)
