I made this same point over a year ago. The same segment of the market that Blu-Ray is targeted at is also predisposed to online downloads insofar as technical capability (broadband) and willingness. If Netflix can ship over 1 billion DVDs, they can surely drive a boatload of downloads.
But more on point is that cable and satellite have reached saturation, so the only way they grow is increase customer value through additional services, which video-on-demand is the holy grail.
Blu-ray won’t enjoy the same decade-long dominance DVD did after it succeeded VHS. But that’s not because there will be other challenger physical disc formats. Rather, instead of buying discs from Amazon, Best Buy or Wal-Mart, people will begin getting their entertainment in the form of digital downloads in larger volumes.