If you read the article, you can see why he thinks the stock will tank. But that assumes Netflix will do nothing in the meantime to maintain its earnings in the face of growing competition. I doubt that premise will hold. They are too big to go down without a fight. I think the analysis is shallow, and one sided. Maybe he has a stake in talking the stock down? Short seller anyone?
In the early days of streaming, Netflix could provide content that no one else could. But that is changing dramatically in the next year, as other large media companies launch their own streaming services.
Netflix will still exist, but they will become more on the model of HBO. As long as their shows are strong, and their rates are competitive, they will be in the mix. They will likely produce most of their own content, and pick up independent films that can be licensed at an acceptable rate.
It will be common for people to subscribe to three or four services because the rates are low, and it's incredibly convenient- more than cable or a satellite dish. Those are the real losers-cable & dish.