I don't see this happening soon (1-2 years from now) because the statistics that are used to make this point aren't the right ones. The post language selector only makes sense when you have a multilingual site and that percentage is not that high. That said the work done in 4.0 are a big step forward.

I believe to make steps in adding better multilingual support we first need to work on the roadmap for taxonomies so at one point we do have native support for relationships. Also we should work on making the current multilingual plugins better and have user tests done to see what users like from all the plugins out there. They are quite different from each other but we could look if they share common code and try to integrate that in WordPress.