MainConcept just released MovieExport, an export plugin for Final Cut Pro, QuickTime and iMovie with a number of higher-end codecs, supporting Blu-ray Disc, XDCAM, AVC-Intra, F4V, iPod, PSP, AVCHD, DVD, etc. So it can get you a bit closer to authoring a Blu-ray Disc, although you still need to have one of the usual apps to create your menus and to do the actual burning, of course.