“Dragon Quest IX: Defender of the Starry Sky” was announced as a Nintendo DS exclusive by Square Enix a few days ago. As it turns out, at that same “20th anniversary Dragon Quest commemoration” press conference they showed the above DS game box that has two DS cartridge slots.
Square Enix is well known for its multi-disc spanning RPG series, so it’s not that odd they’d need more than one of the (over 1 gigabyte in size) DS cartridges. This to make the game look its best, as well as making it contain plenty of CGI cutscenes like the one Square Enix just put on their website: