There is an amazing quote I read over a year ago on the Netflix vs HBO battle and it basically said that it's a race for Netflix to become like HBO before HBO can become like Netflix.
Well, there's more than one HBO-like service (e.g., Showtime, etc., exist) just as there is more than one Netflix-like service (plenty of subscription-based video streaming services exist), but that doesn't stop the fact that Netflix's streaming service is pretty much in the same position with regard to content producers as HBO was when it first ran into premium cable competition, and its route to sustainability in a market where it is no longer the sole player is pretty much exactly the same thing as HBO's was in the same situation -- stop being primarily a route to other people's content and instead become a premier content producer that also provides other people's content, so that you have (1) a compelling reason for consumers to choose you when other services exists, and (2) protection against content producers raising their rates so that all the profit from your business goes to them instead of you.
It's not about them being the only one, but it is about being the market leader. And with exclusive content, there actually "can be only one."
I believe in a mature paid-streaming market, consumers will likely subscribe to multiple services, all for way cheaper than satellite or cable currently costs.
I am going to edit my top level post and add the quote now that I am in front of a laptop.
"I believe in a mature paid-streaming market, consumers will likely subscribe to multiple services, all for way cheaper than satellite or cable currently costs."
Agreed and that's kind of my point - HBO and Netflix can both win big here, it's not really about who can do both content and provision first. If you follow the exclusive content model there can be only one place to watch Game of Thrones or House of Cards but people can (and I think will) subscribe to many services.
There may also be models where exclusivity isn't a given (as it isn't with music services) or that it will just be about content and that streaming will become a commodity, though they're harder to predict (and go against what has historically happened in TV).