Cossacks 3 will be released on 20 September 2016. I have 2 questions.

1) Will Cossacks 3 be available on GOG?
2) When will Cossacks 2 be available on GOG?

I would kill to see those developers use the same engine to make a WW1 trench warfare RTS.

You're best bet is to keep a eye on their Twitter a user asks about gog.

A Steam has pop with the system requirements.

Minimum:
OS: Windows XP/7/8/10
Processor: Intel® Core 2 Duo 1,6 GHz/AMD 3000+
Memory: 1 GB RAM
Graphics: nVidia GeForce 8800 / ATI Radeon HD 2600 PRO 256Mb / Intel HD3000
DirectX: Version 9.0c
Network: Broadband Internet connection
Storage: 4 GB available space
Additional Notes: Screen Resolution - 1280x768

Recommended:
OS: Windows XP/7/8/10
Processor: Intel Core i5-3470, 3.20GHz or AMD FX-6300, 3.5Ghz
Memory: 4 GB RAM
Graphics: nVidia GeForce 560 / ATI Radeon HD 7900 Series
DirectX: Version 9.0c
Network: Broadband Internet connection
Storage: 6 GB available space
Additional Notes: Screen Resolution - 1920x1080