This is from Wikipedia, and it is an interesting theory: <div class="quote_poster">Quote:</div><div class="quote_post"> Since the show is from Tony's point of view, when his point of view ended (gun shot to the back of the head), the show ended. One could say the last thing he saw was his daughter walking through the door.</div> The ending is left open though.
No one knows for sure whether Tony died or not. I would've liked to have a real ending but this ending lets us all imagine our own. We dont' even know if that guy was planning on killing Tony or not. I wish there would've been more action though, it seemed as a plain old episode to me.
When I saw it, what I thought was that it was anticlimactic just like death in real life. Everything in the show is from Tony's standpoint, so it would make sense if the blackout was him dying. So while I would have loved to see everyone die in a bloodbath or something climactic in the ending, it makes sense to think that someone came up from behind him with a gun and killed him.
