The best theory i found while searching HBO's site is this. and im not saying dudes absolutely right. but there were sum wild guesses people were taking about the end and this dude sounded like the most accurate one in my opinion. what chyall think?
First Off I must say this was a beautiful example of david chases writing, if no one saw what i saw im sorry, but we should all look back to the previous episode when Bobby and tony are drifting in the boat, when tony asks bobby what he thinks deaths like, bobby simply says "You dont even know its happening, alls you see is black", if you all have noticed that was exactly what happens, so to end this,
RIP Tony Soprano