And, now that I think about it, even if everyone were nice and obeying, the Witcher developers probably receive the sale dates because the games are also sold on Steam. So they just have to transmit them to their colleagues at GOG and voila.

That makes perfect sense.
Ok well, hopefully the sale will start very soon.

Do they normally start on a Monday or could be any day ? Can't remember last year. I will start noting the sale dates and types from now on though. There are several titles I've been waiting for over 8 months for it to be on sale.

One title I had to wait 15 months before it was on sale. Still, I waited and didn't pay full price. :)

You think it'll be this week or next week?

The Summer Sales that is...

Next week. They'll need to drag out the current sale a few more days. Need to get their money's worth from paying that coder to do up the front page Witcher animation.

+/- roughly 6 days of any of the previous dates.

Next week is the best candidate.
I doubt it will be this week, as they don't put big sales and weekly staff picks running concurrently.
I doubt it will be after next week, as it will be too late to avoid overlap with Steam's big sale (23 June).