I doubt it will fail to come out on GOG, but as usual GOG receives none of the marketing & promotion from the publisher.
I'm sure the publisher feels that visibility and popularity on Steam mean everything to sales success, so they are trying to funnel their customers in that direction. If their customer base is split between more than one platform, the apparent popularity of the game is less on each individual platform. More GOG customers means fewer Steam customers, which translates into less time the game might potentially rate high on the Steam sales charts, up where everyone can see it. A lot of Steam people seem to hear about new games from those charts, and buy whatever is popular on those charts.
In order to sell their games on GOG, GOG should make publishers sign a contract where they commit to promote the GOG platform equally alongside any other platform they use. It's not an uncommon tactic, generally, but I don't know if GOG has the leverage with publishers to use it.