Though there are only a few details, NickNorthStar over on Lead Avdentures forum spilled the beans ahout what to expect:
There will be a frame of 5 bodies (not split torsos) with separate heads and weapon arms.
The heads and weapons are all trying to look evil, with lots of chains and skulls and a vial with something nasty in it etc. This time though there isn't as much arm variant, there are more hand variants. So you'll have to cut a hand off the left arm to glue a different one on.
There will be enough weapons to make two warbands out of the Cultist box set to accompany your wizard. All the heads and arms are inter-changeable with the Frostgrave Soldiers boxed set one, so you can use some of the spare arms from your Soldiers box set to give more variety to your Cultists and vice-versa.
There are also 4 undead heads and 3 sets of Undead arms on the frame as well so you can turn your plastic Soldier or Cultist into a Skeleton or Zombie!
The tentative release date is the 20th of November 2015