This is definately going to happen. I've been saying this for years.
Right now, things air live on tv, and if you're not there you either (a) tape/record/tivo things to watch later or (b) watch DVDs, BluRays or on-demand at a later time.
We're slowly bringing (a) and (b) together.
It's already that way in my household. We have no cable, only over the air tv and an apple tv. For example, my daughter loves Disney's cartoon 'Jake and the Neverland Pirates'. We subscribe to the show, and she can watch every episode over and over again at any time she wants to. When a new episode comes out on the Disney Channel, it's on our Apple TV the next day to view.
I think most shows will be like this in the future - i.e. 8:00pm Monday nights - a new episode of 'How I Met Your Mother' is available. You can get these episodes for $x/year subscription, or a monthly $x/month subscription to CBS to get all of CBS's shows. It's all going this way.
Look to the future, say 2020: The main reason I see content companies (CBS, NBC, HBO, MGM, etc. etc.) going down this path is that people will soon no longer be able to get physical copies of anything (it's all by subscription, and when your subscription ends, access ends) and will not be able to record anything (due to iPad-type locked down devices vs. general use computers not as available anymore). People can no longer buy physical copies to give to friends. Everyone will have to purchase their own copies.
It's going this way, and there's nothing we can do to stop it. There will be numerous attempts at backlash, but 'The Man' will make it this way.... eventually.