There's really no way to "officially" retire from rap. It's something rappers say, and it's something Joe Budden has said for about a year now.
But it seems like Joe has already broken that retirement. The Source reports he laid down some new bars during the cypher at the BET awards, which happened this weekend and will air on October 16.
But if you're looking for some Eminem smoke you're out of luck. In fact, Shady introduced the cypher Joe participated in, and Budden didn't mention him in his bars.
The cyphers are prerecorded and it's possible the Eminem/Budden one went down before Em dissed Joe on Kamikaze, sparking calls for Budden to get back in the booth and respond.