They will wait until they have killed Pakistani President General Pervez Musharraf to launch thier next attack. I have no doubt it will be of the biological, chemical, or most likely nuclear variety. OBL and al-Zawahri continue to operate from Pakistan and they want to make sure that Musharraf goes the way of Northern Alliance leader Ahmed Shah Massoud who was was killed September 9, 2001, by a bomb inside a video camera during an interview at his headquarters with two Tunisian al Qaeda operatives posing as journalists. To this end there have been two assasination attempts on Musharraf in the past week, both of which he narrowly escaped. Once they are successfull at eliminating Musharraf I have no doubt they will launch their attack.
Incidentally if you read the report about the cancelled flights from Paris to LA the suspected terrorists who never boarded the planes are reportedly Tunisian.
Why? Could they somehow get his nukes and use them against us?