A sequel was announced for the Nintendo Switch.
No idea if it's a exclusive or will there be a port for other systems.

https://www.youtube.com/watch?v=Z6RrrQhyLyg

It will be ported for PS4 as well and once BV Engine Software is gonna be less busy (they are working on TotCS4 and the latest YS) they will port this to PC as well, I am pretty sure.

To release on 22nd June: https://store.steampowered.com/app/1933740/The_Caligula_Effect_2/

I don't know whether it'll come to GOG. Edit: oh, then I notice there's another thread.