All the details are coming out, and the latest is that stores will be having an event for Shadow Wars starting on April 1st. Below we have the first details.
via anonymous sources on Faeit 212
Shadow War Details
1) Participating stores will be getting an organized play kit on the 1st
that includes everything you need to play including a complete rulebook
just like the one from the game box.
2) In this game "hired guns" are called "specialists", those are what the
cards you've seen for the Deathwatch Veteran and Flash Gitz are for.
3) The rulebook will only contain rules for Space Marines, Imperial Guard
and Orks. The other faction rules will be on the website.