I am not sure why there is a surprise that DVD still sell. There is about a $10 difference and some of the BDs come with 3D and 3 discs in them making them quite expensive to get the BD. And for a lot of people, the quality just is not there. Guys on this forum are more likely to have a high-end display or projector. Good for you...us! But many more people have a crappy LG 46" LCD and it is placed 2 feet above their couch with mantel in the way. Not too surprised. If NetFlix can grow, then Blu-ray must not be that important to many people.
4K is crazy. Until we are not paying $60-$80 a month for crappy internet, we should not think much will happen unless there is a new disc type coming. I am ready for thumb drive media with huge servers. Maybe you pay $30 for the drive, load it once, authenticate the movie, and send the drive back for a $10 credit to the next movie. Once loaded, it is yours. Mail is cheap, network is too slow, small drives are cheap.