Well, we know that:
LOYALISTS
- Ferrus Manus is dead, surely.
- The Khan is supposed to be enslaved by DE, but I agree with Eldargal here.
- Russ went into EoT, and his armour was recovered in one demon world in one of the Hunts for him by the Space Wolves.
- Johnson is buried in his homeworld
And in the "REBELS":
- Horus is dead
- The rest we know are Daemon Princes