Every 2 weeks on Friday new games (typically 2 games) are added to the coin shop.
Games may also be added in for special events (like the big Sci-Fi thing that saw 3 new games added during the week), but the coinshop adds in new games on a biweekly schedule.
It also won’t replace the current coinshop content, games leave the coinshop once 100% of keys are claimed.