Usher wanted to surprise his many fans with some seemingly "unexpected" collaborations for his upcoming album Looking 4 Myself, which is scheduled for release on June 12th.  This is how he came to team up with A$AP Rocky for "Hot Thing", which was produced by Pharrell.  He spoke to MTV News about his decision to make that collaboration.

"Before it was Luda, after that it was Jeezy, after that it was A$AP.  I really wanted to create something that I felt would work in both our worlds, a fun record that would be a little bit irresponsible.  You gotta just let it go. No apologies, f*ck it."

This is going to be Usher's seventh album.

Source: rap-up.com