just reading the 2018 playing regs and CF say:
Tier 2 - Women’s Premier league:
i. At the end of the 2018 season, we will be moving to an 8-team league, therefore
the top two teams will be promoted to the W-League and the bottom two teams
relegated to Women’s 1.
It also confirms no relegation from w-,league, so 8 team league in 2019 planned