He's been helping other boxers during his retirement, both in sparring and being their second during matches. He's also literally been wearing training weights this whole time while helping people better themselves. He's sparred with Takamura at least once that I can remember and Birdman noticed that he's gotten faster with the weights on even though Ippo himself says that he feels like he's lost a step since stepping away from the ring. In the newest chapter, Volg asked him to be his sparring partner, while also asking him to take the weights off. Let me tell you, Ippo put the fear of god into him during that sparring match
. Everyone watching was wondering why Ippo retired in the first place, while Ippo apologized at the end of the spar because he felt like he didn't help Volg at all.
His perfected Dempsey Roll looks terrifying now.