Blu-ray ought NOT to take off, simply because:
We SHOULD (but not necessarily are) be starting to see sufficient bandwidth to the home that video streaming is the norm, making HD discs the last generation of physical media
Blu-Ray doesn't offer the same huge step up from DVD that DVD offered against VHS. The step up that it does offer comes with a relatively high entry point (new TV, new discs etc)
Business outlook for BD is pretty bleak, as pointed out by the funny post above (everything in dumper... check!)
DVD finally took off big-style because Joe Average could buy one for £30 in Asda. Sure, this will probably happen eventually to Blu-Ray, but we really ought to be streaming everything by then, forget about disc players.
All that said, BT's lacksadaisical approach to infrastructure upgrades, plus the inclination of the media industry to punt physical products using age-old business models means that we'll probably still be using discs of one sort or another in ten or twenty years, and right now Blu-Ray is the one new format gaining any traction at all.