Actually I would have been very glad if other vendors adopted the Dart VM, and we got a new fucking web language to eventually replace (or supplement) JS, instead of the pile of hacks we got.
Besides, I'd much rather have the effort go into one new VM (or VM "mode"), so we can solve the problem once and for all. That is, let's have Web Assembly.
Not some support for other languages on a first class basis on the webpage just like Javascript (which direct access to the DOM and everything).