Although #1 seems to make the most sense
As the US troops approach Baghdad, the Iraqi military disintegrates and Saddam's support crumbles, it's going to be very hard to avoid some variant of scenario #2. Saddam is the most hated man in Iraq, and Iraqi military officers are going to be falling all other each other to curry favor with the new conquerors and to distinguish themselves by delivering the head of Saddam to the Americans. My prediction is that it will be very difficult for US special forces to get to Saddam before some pissed off or simply opportunistic Iraqis get to him first.