Here is the announcement at the bottom of a WarCom article on the Eldar Codex.
This isn’t just an exciting time for Aeldari, but for all Warhammer 40,000 xenos players – after the craftworlds touch down, there’s something gribbly and chitinous coming. We don’t want to say too much right now, but there are lots of them, they’ve come a long way, and they’re VERY hungry. For biomass. Okay, you forced it out of us – it’s the Tyranids.