> Sorry, should I have used VHS, DVD and Blu-Ray as examples instead?
All examples of a technology being replaced (or partially replaced) by a better technology. WebM is not better than H.264 technologically. At best, it is almost as good as the lower H.264 profiles.
H.264 might conceivably be replaced as the dominant de facto video standard, but the replacement will not be WebM.
(BTW, I don't necessarily accept the 2028 number for when the relevant H.264 patents expire. That's when the last of the patents expire, but many of the patents are on the more recent enhancements to H.264. We only need the patents that cover the main profile to expire).
World is ripe with examples of technology being replaced by a challenger due to non-technical factors. The rise of MP3 and other lossy standards in favour of CDs is an obvious example. Early LCDs were not as good in terms of image quality as contemporary CRTs. It doesn't have to be better, it just has to be good enough technically and attractive for other reasons.
Sorry, should I have used VHS, DVD and Blu-Ray as examples instead? 35, 15, and 7 years ago respectively.