From ABC News' Jake Tapper:
Sources tell ABC News that President Obama will nominate CIA director Leon Panetta to replace Defense Secretary Robert Gates. The president will nominate Gen. David Petraeus to serve as director of the CIA.
The president will also nominate Marine General John Allen to replace Petraeus as ISAF commander in Afghanistan, and Ryan Crocker as US Ambassador to Afghanistan, replacing Karl Eikenberry.
The announcements are formally expected tomorrow. An announcement for the new Joint Chiefs of Staff chairman will likely not be part of this announcement.