The way I see it, if you were to draw two graph lines showing the prevalence of H.262 and H.264 over time, it would show of course that H.262 has lasted much longer so far just by virtue of it being older yet still in active use, but the area under the H.264 line is probably already or tracking on being much larger, depending on many factors, such as how you quantify "prevalence".

I don't see H.262 as becoming completely irrelevant any time soon, so it's clearly had a hell of a run, but I expect H.264 to wind up having a similarly long tail. I am not sure I'd bet on it being longer, but I wouldn't bet against it either. I'm only of the opinion that H.264 will have one of the longest of any video codec, but perhaps not the longest.

For sure. Just YouTube alone is a vast ocean of H.264 bits.