Years of effort have gone into making javascript VMs faster than they have any right to be. Even an ideal bytecode would likely be slower than javascript for years. It seems unlikely that many people would be willing to give up performance now for theoretical future performance, and without a reasonable amount of use, there's no good reason for browsers to implement the new bytecode.
For better or for worse, we're stuck with javascript for the foreseeable future.
Even an ideal bytecode would likely be slower than javascript for years -- no, statically-typed bytecode should be significantly faster than dynamically-typed JavaScript (both in execution and parsing time), IMHO.
For better or for worse, we're stuck with javascript for the foreseeable future.