It might blow up in Firefox's face, a long time from now. For now, there isn't even any standard for how the decryption algorithms should be implemented as plu

It might blow up in Firefox's face, a long time from now. For now, there isn't even any standard for how the decryption algorithms should be implemented as plugins, so it's hard to see how Mozilla could implement it in the first place, let alone be pressured into implementing it. Also, H.264 was already dominant on the web when the video tag was introduced, it was far better than Theora, it's slightly better than V8, and as you mention, it has hardware acceleration - all strong reasons for people to use it regardless of their opinion on patents. EME's support is mostly limited to a small number of companies that want to use it and doesn't seem inevitable at all. The situations are very different.