For all that the world-hopping gentleman bandit and treasure hunter Dack Fayden gets up to in the IDW Magic: the Gathering comic series, he doesn't show up in the main storyline or the cards much. Sure, R&D is willing to give him a throwaway reference here or there with things like the flavor text of Artificer's Hex or the art of Bred for the Hunt, but for the most part he only shows up on the comic promo cards. But according to MTGSalvation Storyline forum poster Hyze, background clues on him and his homeworld have been sprinkled throughout Commander 2013. Hyze quotes the French Planeswalker Points page as saying:
"Découvrez Commander !
Toute cette semaine, ouvrez l'œil pour des avant-premières des nouveaux decks Commander qui sortent le 1 novembre 2013 ! Cinq nouveaux decks, cinquante-et-une nouvelles cartes et un nouvel environnement abritant le voleur le plus talentueux du Multivers : Dack Fayden et Fiora, son monde natal ! Consultez DailyMTG.com pour des avant-premières toute cette semaine !"
Rough translation: they're saying there will be 5 new decks, 51 new cards (nothing new), and one new environment featuring the Multiverse's most resourceful thief, Dack Fayden, and Fiora, his home plane.
Now, Dack neither appears in the art nor the flavor text of any card in Commander 2013, and he's definitely not represented as a planeswalker card himself. However, this means that the upcoming "more info on the way about the new legends (both in short-summary-bio form and in longer-short-story form)" that Doug Beyer promised on his Tumblr will probably be revelatory about Dack, probably as a way of testing the waters for future supplemental products. Maybe we'll even see cards directly related to him in future Commander and/or Planechase sets; MTGSalvation poster echelon_house made the intriguing suggestion "If it says a new environment, could it possibly be a "Plane - Fiora" card randomly thrown into every 100th deck or something?"