it went black as Tony was shot in the bakc of the head. Last thing he saw was Meadow walking in the door. The show was from his perspective and went black as his lights went out....my opinion
I think the showrunners never clarified and said it was up to the audience
I also think PAULIE was the one who set it up and was set to take over, remember he turned tony down right before that scene..it was Paulie who was part of his death
this, worst ending ever, hopefully the new season does the show justice