To my mind, it doesn't matter whether a murder actually occurred for Ulbricht's culpability. He thought he was ordering a murder, he solicited proof, he got proof, and he asked for more hits. In his frame, someone was murdered on his orders. It's a burden to prove for sure, but the fact that he paid substantial cash equivalents in bitcoin to me mean he didn't think he was playing some fantasy game with scammers.
The chat logs show that he was quite stoic about the whole thing and treated it as a mundane business action to protect himself ("is a liability and I wouldn't mind if…"; "I've received the picture and deleted it. Thank you again for your swift action.").
Given that he is now free, and may have access to substantial cryptocurrency wealth, I think it would probably be best under the circumstances if everyone forgot about these allegations and just left him alone to live a quiet life.