Forget about DVD sales, that's on its way out. Streaming is the future. Whether there are ads depends on the individual outlet. I don't get why people are willing to put up with ads on Hulu Plus but maybe they get more stuff more quickly that snails-pace but ad-free Netflix. Personally, I'd rather just wait.
Anyway, what CBS should do is put a new show on Netflix and Hulu Plus and iTunes and anywhere else they can get it. Certainly Star Trek
is a powerful enough brand name, especially for the early-adopter tech types who already have streaming subscriptions, that they can laugh off any attempts to insist on an exclusive. The way to make the finances work is to cobble together wide-ranging distribution, on TV and streaming (and DVD sales to the extent they persist).
The problem is, this is all a lot of work for CBS, why not just do another cop show instead and show it on traditional TV? Conversely, the motivation is, ratings for traditional TV are sliding badly, and CBS is finally getting hit by their audience aging out of the 18-49 demo, and it's only going to get worse. Now is the time to start figuring out new business models that will work in the future, and Star Trek
is a good guinea pig to experiment with.