Yes, indeed -- it is on it's way. We had to wait with creating 3.9 docs because of some things that needed to be added in the 3.8 before we could make the 3.9 copy. We'll add 3.9 and the necessary changes as soon as possible. It will hopefully be revealed within the next couple of weeks. As you might already know, 3.9 does not contain big/visible changes but rather a lot of small fixes/improvements (not counting the Website Interface) and thus the docs will most likely be an upgraded version of what we have for 3.8. When it comes to the installation docs, they will probably be the same as for 3.8.
If you're looking for documentation related to the new Website Interface, have a look here:
http://ez.no/doc/extensions/website_interface
If you are wondering about 3.9 specific changes, please have a look at this page:
