The relationship between terrorist leader Abu Musab al Zarqawi and and the mainline al Qaeda leadership continues to deteriorate. Zarqawi's recent audio messages have not only attacked the U.S. and the Shia-dominated government in Iraq, but also Iran. He's even claiming that the U.S., Iran, and Shia in general, are in cahoots to destroy Islam. He has also called for continued attacks against Shia.
Except for his verbal attacks on the U.S. and the Iraqi government, he is almost totally distanced himself from the central leadership. Other al Qaeda leaders have been trying to down play anti-Iranian and anti-Shia rhetoric, and have been strongly discouraging attacks on civilians.
Given that Zarqawi has become a loose cannon and that his actions are handicapping Al Qaeda's efforts, it seems reasonable to expect that an accident may befall him at some point in the near future. If handled right it can be made to look like he went out in a blaze of glory fighting American troops or that he was foully murdered. Either way, al Qaeda gets rid of a problem and gains another "martyr."