We finally have a release date for Return to Monkey Island: September 19, 2022 (formally known as International Talk Like a Pirate Day).
Further more, pre-orders are now open (or will be soon): And, a special pre-order bonus, you'll get a completely useless and inconsequential piece of Horse Armor added to your inventory. Joy.
Another update: The Steam preorder is for both PC and Mac -- purchase one and you'll get the other. Also, the horse armor is truly real, so... who knows what that's all about?!