Hey there,
The next book (on Drivethru before the end of the week!) is Supplement 15: Powers and Principalities (yes, it is leap-frogging Supplement 14: Space Stations!).
We did have someone start a Hiver book, but we have not heard from them in over a year now, so that is likely in limbo.
After Droyne, K'kree are likely next, and we have a great angle for them (after discussion with Marc and his advisors). However, no writer has yet been set for them.