I think that Ippo will probably make a comeback... It's just that he dicks around in his private life & is lacks too much decisiveness, in his life, work, even Boxing. He still somehow feels like there's something he could have done, but because he's too complacent he just says "I'm done & fine with it" when he isn't; If he lacks that drive of pulling together even if he were to be punch drunk there's no way he could stand on the World Championship ring. Also it serves for Ippo & Kumi's relationship to move forward, how many goddamned years have go by and they still aren't "something more"? Ippo must first truly decide and take a step forward in what they actually are & Kumi must realize that Boxing isn't something she should shun off Ippo's life. It is a part of him & she should accept it as most comprehensive as it is; she is looking out for what's best for Ippo instead of what makes him happy, and until she realizes it or Ippo makes her understand that relationship has no future.
My 2 cents