"Breaking news. Return of the MAC. May 13th, working on an opponent, more news to follow," he tweeted on Monday.
The 28-year-old has not fought since beating Ukrainian Wladimir Klitschko to become world champion in November 2015, subsequently pulling out of a rematch twice.
He vacated his WBO and WBA belts last year, revealing he was seeking medical help, after telling Rolling Stone magazine that he had taken cocaine to help his depression.
Fury's licence was "suspended pending further investigation" by the British Boxing Board of Control.