As soon as the masses decide that HTML5 = "Flash, but better", everything that is bad about Flash will rapidly become everything that's bad about HTML5.
Changing the underlying technology will not change the people who use it.
It will be worse. This stuff can't be contained with simple tools like Flashblock. Unless you want to block all Javascript by default, which will probably break 99% websites in the near future.
Changing the underlying technology will not change the people who use it.