Re: "Google may be OK with this but ultimately it's a big risk for them"
Right, but we aren't talking about reality at the moment, someone posited the thought experiment "If JS was to disappear, companies like Google would be up shit creek and they don't seem to acknowledge those risks".
It's more philosophical than that.
It's a bad thought experiment because either there is an equivalent language to replace it, in which case a Dart-to-new lang compiler would remove the risk, or that there are no more browser apps possible, in which case Google write a Dart-to-C compiler and deliver native apps.
Besides, we like fast-moving, new, dynamic stuff. To be provably secure means slow-moving, mature, never changing stuff. Shiny-shiny wins every time.
The only sure solution to the problem of dynamic web pages is to forget about client side execution in the browser altogether, and replace it with a Turing incomplete remote display protocol for code running server-side. A bit like HTML used to be. A bit like X server protocol, and (AFAIK) RDP, VNC, etc. We're not very good at implementing such protocols problem free either (buffer overruns, etc), but it's a much easier challenge.