"Specific and Credible" Terrorist Plot?

There has been much discussion over the past 24 hours regarding a possible terrorist threat to coincide with this Sunday's 10th Anniversary of the 911 attacks.
After reading through more than 35 news articles and several federal agency websites regarding this issue I have extracted the basic facts and worked them into the below synopsis to keep you updated on this matter.

SYNOPSIS

From what I can ascertain, information regarding this threat was initially uncovered by our armed forces back in May when they raided a compound in Pakistan and killed Osama Bin  Laden.
Additionally, over the past several days the CIA has determined that "specific and credible" intelligence exists indicating that:

1.  A terrorist plot may exists involving the use of a vehicle or vehicles.

2.  Three individuals, one of whom is purported to be a United States citizen are involved.

3.  These individuals entered the United States during this past August from Pakistan.

4.  The target of this plot is New York City or Washington D.C. (or both?)

5.  The target date of the plot is to coincide (just prior to, on or just after) this Sunday's 10th Anniversary of the 911 attacks on the United States.

6.  It is believed that the source of this plot is the current leader of al Qaeda,
Ayman Al-Zawahiri, who intends "retribution" for the killing of Osama Bin Laden.