If we take the blackout as an indication that Tony loses consciousness, why don't we think, as he contemplates what's happened, and the gathering of his family, that he's having the same kind of anxiety attack that prompted him to go to Melfi in the first place? If Tony's gang life is the story, surely the plot of the Sopranos is his therapy--therapy which finally fails because he cannot or will not change--nor, for that matter, will anyone else in his world. When Melfi ended the therapy, the show was over. So he's waiting for his family to become complete, it's being delayed by something normal and natural (parking) and he blacks out. He's back to square one after all the blood he's spilt, all the suffering he's caused and all the damage he's done. No redemption, no cure and no resolution of symptoms. Nothing.