[Stop reading now if you haven't already seen the final Sopranos episode...]
My first thought when the episode ended was that the cut to black signified that our window into this world had suddenly shut, i.e. the show was now officially dead. (After all the little hints along this line, like the use of Vanilla Fudge's "You Keep Me Hangin' On" at multiple points in this episode.)
But after a little more thought, I'm forced to reluctantly conclude that Tony really did get whacked. Yes yes, everyone who has that point of view mentions the foreshadowing with the conversation with Bobby about never hearing the shot that gets you, and when you die everything just goes black. But there are a couple of other things that were sticking in my mind already from previous episodes, that I think tie in even more decisively. (After all, clues that everyone picked up on could just be more feints, like all the next-week teasers lately that didn't have any payoff.)
First, there's a common thread running through most of the recent killings on the show. Bobby was killed because he was absorbed in his model trains. Didn't you have the thought when the gunmen came into the store, maybe Bobby will display lightning reflexes and make his escape? Didn't happen. Silvio's getaway from the Bing was delayed by just a few crucial seconds because he wanted to bring along his business ledgers. Didn't you wish that Sil and Patsy would be well armed and great shots? Uh uh. Phil got surprised because he was paying attention to his grandkids. In each case, someone paid the price because they took their eye off the ball, distracted by the thing that they loved the most. Even Christopher died because he was dazed by drugs, and the music distracting him was from the soundtrack of a gangster movie. He qualifies for a two-fer.
What was the significance of Meadow having so much trouble parking? The moment she came in was when Tony would be the happiest and least cautious, and easiest to take by surprise. So that moment was dragged out while we got an eyeful of all the shifty characters in the restaurant.
Some have said that's no good, we don't see the series through Tony's eyes, so why would we experience his point of view if he was being whacked? But remember when Sil was in the restaurant with Jerry Torciano. Reality seemed to go out the window for a few seconds, it was very confusing, and then we realized that we were getting Sil's perception of the scene with time slowed down and the gunshot seeming to come later than it really did. That was a notable departure in the cinematography from previous acts of violence. Which makes sense as foreshadowing, if the finale takes the idea to another level, by giving us the perception from the person who gets hit.