In leaks to reporters, intelligence officers voiced concern that al Qaeda's leadership has reconstituted in Pakistan's Waziristan tribal areas. This area is now considered a temporary autonomous zone (TAZ) due to a truce that Pakistan signed with local leaders (and by extension the Taliban) last year (see "Our Man in Pakistan" for more on the details).
The initial destruction of al Qaeda's hierarchical organization in Afghanistan drastically reduced the ability of the organization to design, develop, and launch global attacks. In effect, it was reduced to media messaging to catalyze organic growth of groups that would launch attacks locally. This has been relatively successful (London / Madrid / Egypt / Thailand / Pakistan / Saudi Arabia and, of course, Iraq), but it has damaged the groups ability to mount a spectacular global attack that gained it so much initial success -- in that it both incented US overreaction in Iraq and catapulted their organization into a global setting.
Here is what this means
The development of the TAZ in Waziristan and the reconstitution of a semblance of al Qaeda's previous organization means that larger attacks can and will be launched. These attacks will come in two forms, based on an analysis of al Qaeda's evolving strategy. The first type, reflects the recognition by al Qaeda that systems disruption has been extremely effective in Iraq. These attacks will likely be against the global oil system -- although rather than take the many small attacks approach used so successfully over the last three years, it will probably be focused on large events like the attempt on Abqaiq in early 2006. The second type might be another symbolic attack against the US like 9/11. With all indications that the US is in withdrawal, a new attack is likely needed to propel the US back into aggressive action (see "Al Qaeda's Grand Strategy: Superpower Baiting" for more on why).
See: "Al Qaeda Chiefs Are Seen to Regain Power" Mark Mazzetti and David Rohde, The New York Times, February 18. 2007 for the original leaked information.PS>Extra credit: what happens when the "doughnut" network described in this exploration of al Qaeda's structure refills its "hole."