Source - Assassin's Creed 4: Black Flag - Steelbook: Amazon.de: Games + Assassins Creed IV Steelbook - Collectors Edition Forums

So it looks like Assassin's Creed IV is gonna have 2 Steelbook designs.
The one from the Skull/Black Chest Edition and Pre order exclusive steelbook

Toggle Spoiler



Note: You can buy the steelbook above for 19,95 on Amazon.de, but those pre ordering ACIV ad Amazon.de will get it for free.