i will try to follow development of 8.4, and write examples of what's possible with it, based on current HEAD code.
of course there is no guarantee that it will work in final, released 8.4 (it is a bit too early to talk about it, but given the fact that the patch got committed, there is pretty good chance we will see it whenever 8.4 will be released.
today 2 new features: limit (select ) and optional as in select.