My prediction for the new 40k starter set:

- all new sculpts (monopose models like soul wars)
- new and exciting redesigned necrons vs. a mixed sisters and space marine force
- Szeras and Draxus included in the box
- basically it will look like soul wars

from a marketing perspective this makes the most sense to me because GWs goal is always to get new customers to buy these sets, and much like Soul Wars I think they will be aiming to include a healthy mix of men, women, and undead all in an easy to build format

if you look at Draxus' characterization as an unconventional leader who will use any weapon available to fight her enemies, it makes the most sense she would be in a box with an unconventional force

also i think a box with just space marines vs. necrons is a boring set that i think less people would buy (especially new players like me) and GW knows this