And seeing as how Blu-ray is nearly dead, when CBS does remaster DS9 and Voyager in 1080p, I wouldn't be surprise that they discontinue the production of bonus features, or only commission 1 bonus feature.
That's pretty noticeable already. When DVD started, bonus features were just that - to entice to viewer to upgrade from VHS, or decide to watch something again. In DVD's heyday, the special features were practically a selling point in themselves. I've got discs where I've never even watched the main feature.
Now studios seem to have realised that VAM is a waste of money for them - people don't watch behind the scenes documentaries on Netflix or iTunes, and they aren't available. It obviously isn't hurting download sales. Even blu-rays don't seem to have as many extras as DVD had five or ten years ago - the STID blu-ray was a good example.
Well, DVD inherited special features from the laserdisc format. For years before DVD even came on the scene, optical disc formats very often utilized special features as an added bonus. The Criterion Collection was the first home video distributor to do this, and it wasn't to "entice the viewer to upgrade," it was to provide a "film school in a box" for the consumer.
There's plenty of blurays that are packed with special features - Jaws was stocked to the gills, all of Ridley Scott's movies get gigantic packages of features, and Criterion still loads their releases whenever possible. It depends on how "big" the release is.