It sounds like the unreleased album was when Katy was signed to another label and then dropped. Based upon that, there's a lot of red tape that both labels would have to break through (licensing, royalties, ownership, distribution etc...). I wouldn't hold your breath that it will be released as often labels lock unreleased albums TIGHT! Also some artists hate releasing their older material as they view it to be immature and not up to their current standard.
I like to think of this album much like Britney Spears "Original Doll" album. A lot said on it, but will never be released