Based on everything that happened in the show, the only logical ending is that Tony is murdered.

A more realistic ending in my opinion, although maybe not a better ending, would have been if Christopher doesn't die off, and instead, finally decides to go to the Feds and testify against Tony, and the rest and cripples the family.

Then he would tell all he knows, everyone would find out what really happened with Adrianna, Richie Aprile, Raplh, etc etc. Tony would've finally got exposed.

It was obvious that it was heading that way and Tony knew it so he used the car crash as opportunity to stop that from happening, but realistically that should've been the ending.