Maybe a small step...the FAA always applies cost/benefit analysis to NTSB recommendations.

In this case the cost is very high and the benefit is saving the lives of a couple freight dogs each year...ie effectively zero benefit in the eyes of big government and their corporate sponsors. At least until a flaming freighter crashes into an orphanage.

Some of the big-name operators may install suppression systems (relatively cheap) just to fend off pressure from their pilots and avoid a public battle over the issue.