From what i read in interviews Ivy, there is a possibility for at least 6 seasons.In the comics they will be at the prison for about 3 years which is where season three starts.

There is plenty of stuff on the web with regards to season 3 previews, you should check it out..

The Mafia Is Not Primarily An Organisation Of Murderers.
First And Foremost,The Mafia Is Made Up Of Thieves.
It Is Driven By Greed And Controlled By Fear.

Between The Law And The Mafia, The Law Is Not The Most To Be Feared

"What if the Mafia were not an organization but a widespread Sicilian attitude of hostility towards the law?"

"Make Love Not War" John Lennon