I'm sure you already know that if you pre-order Arkham City from Best Buy in North America you will receive a voucher to download Robin as a playable character in the game's challenge rooms. That also means the character will likely show up in the game. Whether or not he will be playable at some point in the main adventure remains to be seen, but we already know that Catwoman will be making her debut so it doesn't seem outside the realm of plausibility. Have a look at the character design inside.