With content shifting from owning a "in-your-hand" tape or disc to the Cloud's more abstract notion of virtual ownership, I suspect that Blu-ray could actually be the final physical product for those who enjoy picking a movie from your own shelf.
Like books and magazines, the future for the younger generation is likely to be a virtual world with "less stuff" that you actually can hold in your hand.
Myself, being older and of a collector bent, I prefer now, and will probably always enjoy that feeling of grabbing a film from my own library. I'm old enough to actually remember the days when owning a home theatre meant spending untold thousands on 16mm prints that you projected yourself. We live in a wonderful age where you can grab a blu-ray off your shelf and nearly any movie you want is easily obtainable for a quite reasonable price.
Somehow relying on someone elses server- on your credit with them, on their promise that lhey will always deliver- is for me a step backwards.I don't care how easy it becomes- part of the thrill for me is in the ownership- that particular copy that film which is mine to stick in the player and watch.
Take away the shelf of movies, and it's no longer yours, no matter what the cloud tells you.
That's how it feels to this old film collector, anyways.
I'll be surprised if there is another physical format after blu-ray. I think it's the skies from here on out- which is actually fine for me, as the quality of this medium has reached the point where it will be hard to improve on a picture and sound within the average home without going outside the traditional classic film medium and surrounding you with an immersive new art that won't be a traditional movie anyways.
I think blu-rays are probably the end of the road for traditional, old-school film enthusiasts. You will otherwise have to trust in the mysterious Cloud, and the Man behind the curtain for your cinematic desires.