One good thing Saddam did back in the early days of his dictatorship was to highly value and promote education and develop a strong scientific elite in Iraq.
The top students were sent overseas to the study at the top US and European universities. Many of his WMD scientists and engineers have worked as researchers at such universities and are experts in their field.
The threat comes from this group and it's ability to produce the chemical and biological weapons very quickly from scratch and there are enough nuclear physicists and engineers to produce nuclear weapons in several years given the right source materials.
There may well be WMD materials in Iraq, but if there are not, the regime has the intellectual capacity to produce them quickly if no restrictions were in place.
That is the real threat if Saddam is left in place.
