DVDs and BluRay discs have DRM. Implementing that did not require any changes to the fundamental data distribution network — I can still walk into a shop, pay with cash and walk away with a disc that I can play on my player, which needn't have any sort of network connection of its own.
One would therefore assume that a minimal form of DRM might be simply to transmit video using asymmetric key cryptography, with individual vendors given a key derived from a common route that can decrypt the stream.
Encryption and decryption keys would be protected contractually. So to obtain a key you guarantee you're not going to publish it.
Mozilla would presumably opt out and Google would probably simply reserve it for the binary release. At least in Mozilla's case, I expect they'd provide some sort of mechanism to allow third parties to provide a binary blob that could push decrypted video in place of the normal video playback mechanism. The blob would be much simpler, and hopefully therefore much less error prone to implement, than Flash. There would be commercial value in making sure that someone supplies the blob for companies like Netflix, Hulu, etc, so it's reasonable to expect that someone would.
Of course the scheme can be broken — as others point out, DRM can always be broken because it's an inherently conflicted technology, and I'm aware that both DVD and BluRay have been broken — but as it'd be at least as secure as BluRay it'd presumably be secure enough for content providers to continue to provide content.