I'm not sure why people still believe this. There's plenty of usable material left to release.
Bare minimum, there are sixteen songs with full vocals that were kept off of XSCAPE. Let's also not forget the dozen or so tracks that have been available online for years ("Hot Street," "If You Don't Love Me," "I Am a Loser," "Elizabeth, I Love You"), or the various titles that have been confirmed to exist with complete/nearly complete vocals ("Get Your Weight Off Me," "Neverland Landing," "Wonderful World of Candy," "Throwing Your Life Away"), or early/alternate versions of songs we've already heard ("What More Can I Give," "Someone Put Your Hand Down," "Don't Be Messin' 'Round," "The Toy").
That isn't taking into consideration the material with partial/no vocals that many of us would still love to hear ("H2O," "Shut Up and Dance," "Ghost of Another Lover," "Changes"). And that isn't taking into consideration the dozens of titles that we know nothing about ("D.I.E.," "Lucy is in Love with Linus," "Red Eye," "Craze"). And THAT isn't taking into consideration the titles we know NOTHING about yet.
In short, there most certainly is material left for us to hear. Certainly not the 250 songs that we thought existed way back in 2009, but more than enough for years of posthumous projects. It's the Estate's move whether or not it ever comes out though.