Should add an addendum to that, previewed unreleased material. I'm sure Gucci and Ye have songs in their vaults, but we don't know much about them if anything.
For Kanye, officially unreleased songs are: Can U Be, Bitch Please, God Level, Mama's Boyfriend, Living So Italian, Black Bruce Wayne, and a couple more.
For Travis, there's so much material he or other people have previewed it's getting kinda ridiculous now.
The Travis Scott section on KTT covers most of it, but I count at least 20-25 tracks that exist in some form but haven't been released.
Young Thug is the worst offender because most of the songs he previews seem complete but unreleased.
It's only been about 4 years since Travis exploded onto the scene with Owl Pharaoh and his work with G.O.O.D., but since then he's gone from random Houston rapper to full-blown megastar fucking pop stars and trying to build his own domain. If you contrast his come-up to Kendrick's, Travis basically became a megastar because he can write a catchy hook while Kendrick became a megastar from critical acclaim that translated into public awareness.