I don’t have a definite answer for you, but I would imagine it will be quite a while. Epic hasn’t put out an ETA on it yet, and when you consider that they are still talking about changing the API, they don’t want to be in any way responsible for code that is out of their control that is bricked by API changes.
If you ask me, it doesn’t make too much sense because the blueprint API may need to change as well, and i think if they’re holding out for the API to stop changing, they will be holding out forever. but then, I also don’t work for Epic.
Long story short, if I had to venture a guess, it will be at least a year, possibly longer until that type of thing is available.