When will al Qaeda go chemical/biological?

With the news of al Qaeda's growing strength and training camps in Afghanistan and Pakistan, one wonders what type of attack they will go for next. Considering the ease with which Japanese religious fanatics attacked Tokyo subways using chemical weapons in the past, it seems likely that they will go for a chemical or biological attack next. Of course, they could also collect H5N1 samples from infected areas and spread them throughout the west.