Might be better to transplant now but that is a difficult call. The plants will have a better chance over the winter as they will have been established for a number of months, but that depends on how the rest of the summer would go.
In zone 6, I don't think you will need to worry much about protecting them, as long as they are in a rapidly draining mix and the containers do not sit in water. Porcelain pots are generally OK here, as long as they are not full of water when it freezes.
