It seems that the upgrade promised at the beginning of the year has been made available on Steam on January 27 judging from this page: http://steamcommunity.com/games/244430/announcements/detail/231142125568569395

Is it planned to be released on GOG?

I want to ask the developpers directly through their forums, but I wanted to know if it was possible to get an answer from the guys at GOG first. I don't necessarely want to know when it'll be released. Just if it's being worked on.

Judging from that changelog, this version has a lot of improvements, so I really hope it'll be available on GOG.