A girl in Tacoma, first time offender, killed a guy on a bike while drunk (barely) and she got 7 years after pleading guilty. Same basic deal, so I would expect him to get 7 and serve 4.
Putting him in jail doesn't bring P-Stone back -- and let's be clear this was an accident, he wasn't trying to kill him --but if you do the crime, you have to do the time.
Also some people were posting about his widow, I follow her on IG she seemed 100% OK with the KOTR tribute -- she knows who she was married to and she was down with him -- but it's also obvious her life has been ripped apart by Preston's dead. (I just checked her FB and she linked to the episode with a lot of <3s, btw.)