I dont really think that that's a possibility. If anything, maybe it's a dream of his. It's still hard to account for the fact that he sees himself wearing different clothes when he first walks in the diner.
After the 85+ hours of the Sopranos and it's character study of Tony, I really dont think T would accept death at that point in his life. Maybe 10,20 years down the road. But, AJ's still a ****-up and Meadow's just starting her career and a family. They need him too much.