Re: Would you put him in PreK?
I might wait a year as well. What about signing him up for some other activity just to add to his socialization? Do you have a YMCA near you? My oldest did swim, sports, and cooking classes there on and off before he started preschool. They also had a once a week drop in "Preschool Sizzler" class. It all really helped him to be confident on his own and transitioning to a 3 day a week preschool was a breeze.
Wife to Bob, and mommy to Ben and Matt. Love my boys!