A lot of songs that were in the best album are actually being released three times. Almost all single songs (ARIA, Lacrimosa, sprinter for example) are in their respective singles, the album, and then the best album. The only thing that makes they different than Alleluia, Kimi no Gin, and misterioso is that those songs are already in their own respective album (ARIA in seventh heaven and Lacrimosa in Red Moon) before the best album. I'm with grunty - as long they have tie-ins I'm pretty sure they'll make it to the new album when we get one.
I won't really mind few new songs as long as they come with quality. After Eden has 10 new songs if you include symphonia but almost all of them are blah imo. Quantity doesn't always come with quality, after all. Anyway we're taking it too far with discussing a nonexistent album when we're getting a new single with 3 new songs. Just focus on what we're definitely getting.