If I made a business that sold cans specifically designed to hold coca-cola beverages, and they decided to make their own beverage holders, there isn't much I can really do. I could sue, but they'd laugh at me.
If Microsoft stopped using CD-ROMs to distribute Windows, I doubt they'd get sued.
The idea is having a service that everybody uses (fine, Coke). Then, you have lots of major companies develop products revolving around the product. Say, straw makers and ice cube makers (ignore the fact that they can be used for other drinks for now
). The companies' businesses revolve purely around your product. Then, you decide to start including ice cubes and straws with your product, effectively driving all the other companies into bankruptcy.
That's pretty much what this is: if Microsoft has a good anti-virus product included in the OS, then all the companies that provide them will likely not survive. That's scary.