There is NO WAY that Tony gets flipped. The FBI goes after bosses, see Johnny Sac, they don't try and flip them.
I'm starting to agree that killing tony would be a cop out. I wouldn't be surprised if the show ends with Tony behind bars, when was the last time we heard about the RICO case against him? Or with Tony, still as boss, AJ working with him, or something like that.
Who knows? Could go in any direction.