A card with a status of not yet released in the TCG or OCG refers to a card that doesn't yet exist in the format in question, but has a confirmed debut. It is sometimes possible to own a card before it is officially released (like from a Sneak Preview Event or an English Duel Terminal). However, it is not considered a legal card until the release date.
This status is by definition temporary, so the lists below are constantly changing, and may at times be empty.
Unreleased OCG cards
Unreleased TCG cards