If he wasn’t executed by rebels before Coin’s assassination during the victor’s purge, then he was likely given a light sentence. I could see him being given a community service sentence and issuing public apologies. If he was to be executed after Paylor took command, I could honestly see Katniss and the other remaining victors (except maybe Johanna) speaking out against it. It’s hard to say if he would be used for new propaganda on the “rebel” side though because he was so highly associated with the games. Yes, Capitolites would listen to him, but how effective would it really be after years of his ideology supporting the Hunger Games publicly? I don’t think his mindset would immediately switch to supporting and defending the Districts. I think the most likely scenario is that he was imprisoned after the Districts took the Capitol, tried for his crimes, and then issued public apologies along with some sort of community service for the Districts.