It's not actually possible to "plan" a GOG release as such, because their curators manually approve/reject every single game on the site. We submitted it for review months ago and it was rejected with no tangible reason given.
There is a glimmer of hope, however. You can vote on the Lucy Dreaming GOG wishlist here: https://www.gog.com/wishlist/games/lucy_dreaming :)
Thank you very much for the kind answer! I have already wishlisted your game on gog and I will wait a little bit, hoping it happens. But the platform is of secondary importance, I am really looking forward to enjoying your game!