I've written about the different release scenarios here:
https://www.gog.com/forum/general/the_monkey_island_games_to_get_true_conclusion_to_the_original_trilogy_later_this_year/post140 It all boils down to what Devolver intends to achieve by not announcing anything, and there could really be many reasons, or a combination of those:
Avoid infringing on Steam preorders Devolver has a shot at the Big Whoop here. Valve gives a bigger cut of the proceeds if you sell a certain number of games. If people buy/preorder on GOG, Devolver will get that bigger cut later.
Avoid Day One Piracy We all know where these GOG exes end up minutes after release, because one in a 1000 goglins is a complete douchebag, and one in a thousand goglins is more than enough, sadly.
Avoid initial Review Shitstorm Return to Monkey Island's graphic style seems to have "personally insulted" a few nostalgic fans who seem to be better at hating games than they are at loving them. Now, this negativity is the same and possibly even worse in the Steam forums, but on GOG, people who don't own the game can write reviews (impossible on Steam for good reason), and they can also downvote positive reviews (which directly demotivates people to write positive reviews at all). There are zero safeguards against review bombing save manual deletion by GOG personel, and those usually don't even have the time. Last time I reported a review (for, no exaggeration, ugly and politically motivated lies), I got an answer three weeks later. It's frankly not a good look for GOG.
Concentrate on just two platforms on release day Simultaneous releases on multiple platforms are difficult particularly for smaller companies. I've lived through Telltale trying and frequently failing at simultaneous releases, and a few years later, Red Thread Games tried and failed.
GOG sales are thought to be negligible Back in 2017, Ron Gilbert achieved rock solid 6% of Thimbleweed Park sales via GOG. But let's face it, the platform was in a much better place five years ago, dealt much more in the AA's and AAA's.
If Devolver/Terrible Toybox are actually doing physical PC releases that are not just a few trinkets and a "Steam key" in an oversized cardboard box - and those were teased at this week - there's simply no reason for them not to release on GOG.
The question still is WHEN. WHEN THE FUNKY MONKEY.
Personally, I'm biting my nails down to my knuckles right now. I really, really want this, and I really, really want this on release day – it's Talk Like a Pirate Day for fuck's sake, and I want that preorder bonus ... as wonderfully senseless as it is.
I'm actually hopeful because Devolver and Ron were asked the question on twitter a dozen times and took great care to not respond at all. Hopefully that's because a day one release is actually in the cards.