DVD was a once-in-a-lifetime home video revolution. It won't be repeated on blu-ray, and it won't be repeated on any next format, just like it wasn't repeating with VHS, Beta, or Laserdisc. The sales revolution that DVD brought was the idea of people buying movies. People tended to have relatively small collections of VHS tapes or Laserdiscs, and a lot of movies weren't even priced for the sell-through market, they were meant to be rented. When DVD came out, they made it a collectors market that targeted sell-through, and even regular people who only had 25 VHS tapes over the span of 15 years now amassed 150 DVDs in less than half that. The fact that there haven't been rental chains in the better part of a decade certainly helped this along.
Part of it because the picture/sound difference between DVD and VHS was huge, part of it was because the idea of special features was new and exciting and part of it was because the availability and afforability created a new mentality where people owned and watched every movie they liked. That's not being repeated with Blu-ray; the picture quality is not the same step up (even though it is in resolution), and there isn't sufficient reason to buy for special features if you already own the DVD special editions. So, they are content with their DVDs and aren't rushing out to build a huge blu-ray library, let alone replace their old one.
The DVD market is fading away rapidly, so I feel like nowadays if people buy a new movie or a movie they don't already have they are more inclined to get the blu-ray, which now often come bundled with the DVD version anyway. But because people already collected hundreds of DVDs building up a library, they aren't going to replace all that. It's easy to replace 50% of your 32 VHS tapes, but much harder to replace 50% of your 132 DVDs.
