I think at the end of this arc, Saitama will get the hero name One Punch Man and be promoted to S-rank, maybe possibly even S rank 2 or something, which will lead into the next arc with Blast finally showing himself to see who's threatening to take his place.
I think it might be cooler than Saitama getting the title name right at the end, I'd personally love to see an arc, or at least a final fight or something, during which Saitama as seen as the ultimate hero One Punch Man, fighting against the ultimate villain (god?)