Some people have asked me that, and my answer is possibly.
As I understand it, dvd+rw-tools supports burning Blu-ray discs. BashBurn uses dvd+rw-tools to burn DVDs so in theory it should also be possible to burn Blu-ray. None of the developers own a Blu-ray burner however so we cannot test this, but it seems fairly likely that it should just work. So there you go.