Bin Laden + Al Zarqawi = 2 Mahdis maybe?
"This will put a twist on things, aren't they looking for 2 Al Mahdi's at the same time? On the same lines as the two witness in the Holy Bible."
I think some Muslims believe Jesus will return with the Mahdi and reign with him. While Muslims do not accept the Deity of Christ (the Trinity is not seen as an incarnation of the Creator, God taking human form, but as three-God polytheism), unlike most Jews, they do seem to accept Him as a messiah (political, not spiritual). They believe in the Virgin Birth but not the Crucifixion - - go figure.
As to your question - - the two witnesses (Moses and Elijah, Enoch and Elijah, or two others in their mold) are not sent to rule but to witness the end time events as during the transfiguration and serve as prophets.
I'm no expert, and even if I were, trying to explain mainstream Muslim beliefs by looking at the books and tapes popular among radical jihadis is like trying to explain the basic beliefs most Christians share to someone who has never heard them by looking at the teachings of the Aryan Nation and the Christian Identity Movement, who contort Bible verses to justify their pathological hatred for Jews, Blacks, Catholics, and basically anyone who does not subscribe to their belief system.
The lunatic fringe does not define the norm. So I'd always be careful of anyone who seeks to explain or speak on behalf of over a billion people. Jihadis do not speak for Islam, but they are seeking to create a situation where they will.