So I don’t have any direct knowledge. But the term Battlebox was used. Also “water and fyre” follows some of the other Battlebox styled names. Piety and Pain, Wrath and Rapture, and Shadow and Pain for examples. As such I personally would bet 100% on just a Hero and and older units for each army should it happen.
Likewise it isn’t common for them to have the same number of releases at all. Piety and Pain had Sisters and Drukhari. Drukhari got only Lelith, while Sisters got what 2 heroes, a tank, a bodyguard unit and more?
In the same vein Wrath and Rapture was a precursor to the updated Slaanesh daemon line while Khorne hasn’t seen any such additions or new sculpts. And Shadow and Pain gave us the new Melusi Ironscale, while Slaanesh once again gave birth to an entire host of mortal units after the fact to accompany the Lord of Pain. Daughters got what Endless Spells only?
There’s no reason to expect both factions to get equal treatment.
Also I want to thank everyone for the worries about my sources “identity” I’ve reached out to him and given that’s all I’m giving he said it’s fine. And he said if he has anything he can share about AoS specifically he will direct me to post it for you guys. Truthfully though he hears a lot more about 40K releases due to how aggressively GW is trying to get it out.
Oh and he said “Death” in June. I took it as Bonereapers. But he didn’t actually say Bonereapers. I totally forgot that there are credible Nighthaunt rumour engine pics, so take that however you will. Sorry for the assumptions on my part. I will be direct with information now and not try to fill in the blanks.