No, I think they're saying next season will be the last one. Of course, they've said that about the last 3 seasons, so who knows?
I haven't seen any of this season, but if any show would have the nerve to kill off its main character, it would be the Sopranos. I honestly think the show could survive without Tony, it's just got so many great supporting actors.
I think it would be OK if they brought in another character to replace Tony. I don't think they could do it in one hour, but maybe a few episodes into the next season, depending on who it is. I wonder who could replace him??