Warhammer: Chaosbane will be getting two beta phases before it releases Bigben has confirmed, though these will be exclusive to those who pre-order the game. The first of these phases will be taking place in March while the second will follow in April. Those who do partake in these beta sessions will get four legendary crates and an experience bonus for characters.
Details of exactly what the Chaosbane betas will contain will be confirmed closer to the time though the beginning of the campaign. Warhammer: Chaosbane will be released on June 4th for PS4, Xbox One, and PC unless you have the Magnus edition which gives access from May 31st.
Source: Press Release