Jack will be returning to "Fables," that Snow and Bigby will be exiled to "Jack of Fables," and other hints. The letter read thus:
Karen -
Don't let Shelly give all the great Fables crossover secrets away at the panel. You know how nervous she gets speaking in public and how she has to hit the bottle for four or five belts beforehand. Definitely don't let her reveal that Jack will be sneaking back into the "Fables" book, or that Snow and Bigby will be exiled to Jack's book. And we definitely don't want her to blab about the new Jack Frost and his relation to our current Jack, or what happens when Jack ends up babysitting Bigby and Snow's cubs.
Basically, Karen, don't let Shelly say anything.
-Bill Willingham.