Format wars happen between roughly equivalent formats.

HTML5 is wider, better, open. This more like a format execution IMO. Flash was fine when it was the only way to easily do fancy sites. This will change. As always, a few major sites will keep it going for a while and, as always, when a major enterprise switches, because of costs, the white flag will wave.

Besides, we, the users, will benefit from format wars in the end.