Unfortunately html5 is not ready to replace it.
eh. Perhaps that is the wrong way to look at it, I'm sure there are some games and such that flash can do better than html5. Flash certainly does ads well.
I think a lot of the support for Flash to stick around is from people who make money off of writing things in Flash, so there is a lot of resistance from them because, well that is where they make money, and its easier to keep doing that than learn something else. Flash is such a POS from a security, stability and optimization standpoint.
You are right that html5 isn't ready to replace it (I guess), but that isn't because flash can't be replaced, its because there is no real motivation for people that make money off of their Flash products to change. The consumers are the only ones that can speed up this change, and that isn't happening.
The real problem is: Consumers aren't demanding Flash cease being used. We see how html5 is now offered on almost every video site either completely or as an alternative to flash (esp for mobile devices), so the industry can change (video sites are the main example) if there is demand. That demand occurred by Apple not allowing Flash on iOS, there just is no backing from the general user base on non mobile devices (computers).