O-o; KH3 has yet to be officially announced. Those games are just side ones exploring different aspect of the KH universe. Birth by Sleep seems to be a prequel, where as Coded deals with King Mickey and 398/2 Days 9or whatever it is called) takes place during the end of KH I and up to the end of Chain of Memories.

BTW that is not Zack from FFVII, I know little of Birth by Sleep, but I assume this fellow will be one of the playable characters in it.