Will it be released later on? Yes there is CryEngine SDK, but it's not like you can make maps/mods and then import them to Crysis 3.

Good question, dude! I too would love to know the answer to that!

A mod SDK was confirmed a while ago by an engine dev in an interview, but he said it wouldn't come right on the launch. It will be just like Crysis 2, wait a little for the SDK.