They may be trying to kill physical media, but there are still TONS of people that buy them regardless of what anyone things. Yes, streaming is something people love to use, but that's with netflix and such being pretty cheap IMHO. When EVERYONE has their own service and is limited to their own content you'll see a shift in what people want.
As long as Vudu, itunes, Google Movies, Amazon Prime, Netflix, Hulu, etc. have movies from just about every studio, streaming will still do well, but won't take over. I don't think we'll see that trend continue as the studios get more greedy.
"Buying" a movie from a streaming service like the ones I mentioned above makes no sense in the current environment. You do that and they lose the agreement with the studio that produced it, you no longer "own" the movie. Dumb.