I read from somewhere that 3rd part should've been out during summer, but it hasn't come out yet.
I prefer to play games which are finished with expansions, so I can play the whole thing.

It´s in the actual game descriptions here on GOG and it´s wrong.
3rd part just came out THIS month and the last part is listed for winter 2020 over on Steam.

That´s
TWO
THOUSAND AND
TWENTY

Yeah, Stardock, see ya next year.