I would love to know also. But until someone at MS announces something we are all in the dark.
I can not seem to get my 930 to get the latest build, I can get the 166 but then the insider app stops working and updates from the store all fail. So no step to the 512 build from that point
I spend all last day at it, resetting, clean installs, resetting, recovery tool etc. but no luck in making the second step.
So I need to wait for a new build that allows for direct upgrade from phone 8.1 again to get windows 10 mobile on my 930