I think sooner or later a more agnostic VM in the browser will came. HTML was for hypertext, now (almost) it is for general UIs.
The problem is how to make a standard if organizations like Mozilla are not part of that? I think it is not so difficult: don't have a VM? emulate it with asm.js. Do you have a VM? run your application at full speed in more advanced browsers. When Google Chrome came with a faster Javascript engine, others needed to catch up.
The problem with this idea is that a new, "better" VM doesn't offer any substantial benefits over using Javascript-as-a-VM. The limitations of JSaaVM can be can addressed more easily by simply improving on the existing infrastructure. There's not a good reason to throw out what we have when incremental improvement gets us to pretty much the same point more quickly and with less pain.
The problem is how to make a standard if organizations like Mozilla are not part of that? I think it is not so difficult: don't have a VM? emulate it with asm.js. Do you have a VM? run your application at full speed in more advanced browsers. When Google Chrome came with a faster Javascript engine, others needed to catch up.