When there are no versions of a game within the next days after release on GOG there will be no more activity in this direction within the next years. I know this is not true for all and everything, but that describes absolutely correct my experience: No Metro, no Tropico 5, no Dungeons 2, no Dying Light, no Star Wars: Knights of the old Republic 2 and the list grow longer everytime there is a new release for Linux.
I'm quite sceptical too. I'm thinking about buying Saints Row 4 on Steam, because it has a Linux version and I'm not convinced that any version (even only the Windows version) will come to gog.
Edit: Even the OSX version of Turok is still missing.