In a new, authoritative book by Matt Zoller Seitz and Alan Sepinwall, the Sopranos creator David Chase appears to make an accidental confession on THE SERIES FINALE, DO NOT READ IF YOU HAVEN'T FINISHED THE SERIES...
Sepinwall: When you said there was an end point, you don’t mean Tony at Holsten’s, you just meant, “I think I have two more years’ worth of stories left in me.”
Chase: Yes, I think I had that death scene around two years before the end … Tony was going to get called to a meeting with Johnny Sack in Manhattan, and he was going to go back through the Lincoln Tunnel for this meeting, and it was going to go black there and you never saw him again as he was heading back, the theory being that something bad happens to him at the meeting. But we didn’t do that.
Seitz: You realize, of course, that you just referred to that as a death scene.