If you want to sign up for the beta testing, you can by following the link on the Cossacks 3 website. Applications for the first wave of beta testers will be filtered based on gaming specifications, PC specifications, age, etc. Those who are not invited to the first wave will still have a chance of testing later on. GSC are planning on having several waves of testers in order to iron out all the bugs before release.
The development of Cossacks 3 hasn’t all been smooth sailing. Commenting on their Facebook page at the beginning of the month, someone from GSC said:
There is still no release date confirmed for Cossacks 3 but the website speculates release will be somewhere at the end of 2016 with preorder estimated for July - August. The price is also TBC.