It's available now, although the docs (still...) apparently haven't been updated:
In my own apps, I concatenate a list from both versions into one list, then present them to the user as one (while still needing to keep track of the version, since you apparently have to send it when running the API method or it will default to 4.x). Not sure if there's a more elegant way, though I suppose you could just present them as two separate lists in the first place.
