Exactly Crockett...Thats what happened IMO. David Chase emphasized this in the first episode of season 6B, and the previous episode to the finale. He gave us all the hints, and this is the only logical ending I can come up with. We see camera shots from Tony's point of view several times as he comes through the door, and this was his final shot. The 6-7 seconds of blackness was part of the episode. Didn't go to credits immediately. Furthermore, this was the only sopranos where no music was played during the credits.
Tony is dead.