noun which may take the genitive case particle 'no'
not yet on sale; unreleased
Used for products, media, or tickets that have not yet been made available for purchase. Often appears in attributive form with の.
That game is not yet on sale.
Information about the unreleased new product was leaked.
発売予定 means 'scheduled to go on sale', implying a planned release date, while 未発売 simply means 'not yet on sale' without specifying a schedule.
A compound of 未 “not yet” and 発売 “release for sale.” Both components retain their ordinary readings.