Who's part of Def Jam? Cause DJ Mustard is part of Roc Nation/10 Summer Records.
2 Chainz
Afrojack
Alesso
Alessia Cara
Big Sean
Frank Ocean
Iggy Azalea
Jay Z (?)
Jeremih
Jhene Aiko
Justin Bieber
Kanye West
Leona Lewis
NeYo
Rick Ross
Rihanna (?)
He's discussed his Britney collab relatively recently and seemed enthusiastic about the track, so let's not act like it would be out of this world for it to be released soon.
My bet is on Britney, they worked together and didn't he said that the collab was coming really "soon"? I can see the last letter being an "Y", the first One tho doesn't seem like a "B". The feature has to be Big to announce it Like that!