MonDieu I'm sorry, but I really feel like that is a very misleading blog post from Cocoon.
In my opinion (and just my opinion), Cocoon is not gone because HTML5 is not strong, but because it's getting easier and easier to use other tools to export HTML5 and get good fps doing it.
Naturally, computers / devices are getting faster and faster and the speed between native and HTML5 for 2d games is blending.
I genuinely feel that there is really no need for Cocoon because of this and therefore no one really wanted to buy the service (to remove the Cocoon logo etc.), and it stopped being a viable business idea.