If left untreated, yeah. But given the fact that people are now being blasted with antibiotics the moment they find some talcum powder on an airplane, it's not likely that many people who have been exposed to airborne anthrax are going to remain untreated for very long.
So far, we seem to be doing a great job of identifying actual exposures within hours of their occurrence, and rushing antibiotics to everyone who was within a hundred yards of the place. As a result, it's unlikely that many people are even going to get sick, much less die.