I think there must be a security or political reason that Bush doesn't want to reveal what they know about the whereabout of the WMDs...
I think HE is more intent on winning the war on terror, and stabilising Iraq...than proving he was right...especially since at this point we can't get into Syria and look for them (if we haven't already gone and found them)...
Bush is looking LONG term...and I am sure there is a lot that the Pentagon and even the State Department are reluctant to be made known...
Kind of like the NSA wiretaps...
The Pentagon does not want to atagnoise Russia, the "Former" USSR, or China right now.