Flash Animation was made possible by technical limitations as much as by technical possibilities. 480p Flash clocking in at less than 100kB vs RealPlayer needing several MB for the same amount of content in 240p is a huge difference on a slow connection.

1080p streaming in real-time is "good enough" and YouTube will not only host it for free, but even share ad revenue. You could deliver vector animation in HTML5, but a pure animation platform will have a hard time against something that can do both animation and camera recordings.