Before I get into my random theories, I just want to say that the Bobby murder in the model train store scene last night was one of the best in T.V. history.
Theory Number 1: I am expanding on a theory that my brother had, and predicting that on next week’s Sopranos there will be a terrorist attack that kills Phil Leotardo. It has been foreshadowed with the Arab men plot line and what A.J. was learning in college and what A.J. has been watching on T.V.
Theory Number 2:  Paulie kills Tony and becomes the defacto Boss/Phil's puppet.
Theory Number 3: Tony kills himself. This has also been foreshadowed with Carmela's comment about the Sopranos curse.
Theory Number 4: Tony becomes a rat to save himself and his family.