Had James Gandolfini not died, I'd be all for some sort of special one off episode or even a mini series. But you can't bring back The Sopranos without Tony Soprano. Especially not with AJ running things. He was such a monumental fuck up that to put him in charge of anything would be so far removed from the original show it would be verging on parody.
So, I don't think a new Sopranos would work.
Unless it was some sort of spin off where the show would follow one of Tony's underlings living in Miami or something in witness protection and trying to stay out of trouble with the law. Hijinks would ensue, of course, and word could get back to New Jersey that this rat is still alive. It could be a decent way of bringing back some of the great characters from the original show without being tied to The Soprano family so the writers would be free to do their own thing.