Yours is an argument for a high-level, typesafe, compiled-to-native and compiled-to-javascript language. But IMO the argument falls down when applied to C++, because it is not high-level, it is only marginally typesafe, and it doesn't compile to javascript well at all (tradeoff of either massive performance, or missing basic functionality like 64 bit ints).
It is very possible that no language will fit this role exactly for some time to come. But, to me at least, it is very clear that C++ is NOT the language for the job.
This was well-solved a long time ago so...uh...yeah I guess? With much worse hardware?
Maybe Lua?
Do you actually have a real example, or were you just listing off all the magical platforms?
EDIT:
Ha, you do some pretty cool work.
Anyways, put more mildly, is there a case you've seen where you actually have to support all the platforms you've mentioned?
(I seem to be making all sorts of friends today. :| )