It would be one thing if TW were the only content provider out there but they're not. If apple were to buy any media company the others would be less likely to deal with them and start cutting them off. Apple creates products to view content with, they don't create content themselves.
If apple were to buy TW and I am not saying Apple will, but if they do, the market will be driven by customer demand. Enabling part of the market true IPTV experience will start pressuring cable companies to open up. Since IPTV is arguably superior technology customers will demand and in case when they have choice will prefer true Apple TV like services over traditional cable.
At the right price point, buying a current content provide would turn out to be a good move.
