Probably just a peaceful exile.

Just looking at the sequence of events, it really looks like he seriously overestimated how much support he'd have. No one outside Wagner supported him, but once you cross the Rubicon there's no going back. His choices were surrender and get hanged for treason, or die fighting - he knew he was fucked but had no exit.

Putin didn't have any options either except to respond with zero tolerance for treason - any other response massively undermines his legitimacy. He couldn't be the one to tell Prig that he could leave with his life if he stopped, but Lukashenko could 'broker' that kind of agreement without making the Russian government look weak. So Putin makes that call to Minsk and then suddenly Lukashenko's offering that way out.

And thing is, it's probably fine to leave Prigoshin alone. The man shot his shot and left with his tail between his legs. He's lost all credibility with his power base, broke the trust of the Wagner mercs that were loyal to Russia and failed the ones that were loyal to him.