I think your optimistic view misses something important: nomatter how well browsers can execute JS, it's not truly general purpose computing as long as the stuff beneath the browser - from OS to hardware - is out of your control.

It's great that the in-browser ecosystem is expanding and improving, but IMO we will still lose The War if we cannot tell our chips to do whatever we want. I hope we won't settle for the browser when we can and should have it all.