The ending, if there is an ending, is that Tont becomes a nervous wreck, suspecting assassins, traitors, cops, etc. all over the place. Here is what I posted to the IMDb message board:

The inconclusive ending was brilliant for syndication purposes. Basically there was no ending. It made the syndication more valuable because had there been a definite conclusion (Tony reigns supreme over the Jersey mafia, or he [and his family?] get killed, or he is jailed, or he joins the witness protection program; etc.) it would cast a pall over the series. That is, it would spoil the enjoyment of viewers watching the repeats; they would be distracted by knowing how Tony ends up. Without an ending, the viewers can pretend/fantasize/puzzle over their own various endings; it keeps the experience alive.. ... .... ... Also, they can now do a movie or have another season if they feel too poor. ... ... ....Also, as someone else has posted, the ending showed that Tony would have to watch his back and worry about indictments, jail, traitors, assassins, etc. for the rest of his life -- the tension we all felt for the last 5 minutes, he'd feel for the rest of his life.

http://us.imdb.com/title/tt0141842/board/nest/76600677?d=76600677#76600677