So I'm bored, and thought let's jump on the speculation train since there seems to be a void of "what is known" for upcoming 40k right now.
Necromunda is coming of course, I believe Warhammer Community said in November. And GW's Facebook page seemed to hint that the next Codex dropping is Eldar.
So I got a couple of theories as to which models are upcoming for 40k... these are just some guestimates.
1. New/Redone Eldar
I could see them dropping something to go with the upcoming codex.
2. More Necromunda
Maybe some more gangs are in the works. I heard it said somewhere four gangs would be ready at launch, but which ones?
3. Sisters of Battle
There is that wonky salty rumor, but beyond that I've never seen GW hint at SoB as much as they have this past year. At least the community team seems to understand they are wanted.
4. Slaanesh Eldar
There was that interesting image in the Xenos Index that had a missing "branch" of Aeldari that seemed to represent Eldar in thrall of Slaanesh.
5. Emperor's Children
Past year has had Thousand Sons, then Death Guard, maybe Emperor's Children are next? Fulgrim sneaking his way into model form?
6. Dark Angel Primaris
If I had to pick a codex-divergent chapter, I'd pick this one. An easy Primarch to return and this chapter has been ignored for some time. I could easily see them redone but Primaris-ified.
7. More Primaris
If they are the new poster-boys they may need more stuff than they've got now.
Anyway, those are my ideas. I'm leaning on something Slaanesh as it is easy to coordinate with AoS as well, and some of the unresolved rumours appear very Slaaneshy to me.