Interesting b/c in an interview w/David Chase, he stated that there was no definitive ending, that he left it up to the viewer to decide what happens. He also stated that he has no plans at this time to continue w/a movie. However, he also said "I never say never!".
However, another news report stated that Steve Perry was the only one (aside from cast/crew/writers) who knew how Sopranos would end. When Chase approached Perry about using his song in the finale, Perry insisted on knowing how the song would be used b/c he didn't want his song to have any bad connotations attached to it after the final episode. Perry said the song wasn't written to have a bloodbath go on during it, etc. He didn't want any negative portrayal while the song was playing, which leads many to believe that nothing bad happened to Tony (ie: no mob hits, etc.).
Many believe that the ending was that Tony will constantly be "on the lookout" ... watching everyone who comes through every door. Others say it's the death thing. Others say he'll continue his lifestyle until the end.
Really, who knows!? I think the choice is up to YOU!