What? If you are on 4.x you don't need to buy a game at all to use gateway, only the 9.x users would need to buy one.
The 4.x users could trigger the new exploit via rom, but there is no need doing that...
4.x has a lot advantages over 9.x users
- if the trigger is a game, than 4.x don't need to buy it, the main reason to buy gateway, is because you don't want to buy games
- if the trigger is a game, than you need to get the game first, some people don't have access to all games through regional restrictions and nintendo will remove it almost instantly from eshop
- you don't need to update your system nand, only emunand needs to be updated
- if you are on 9.x you will still need to make a 9.x emunand or you could not install any cia (your system nand doesn't have signature checks patched!)
- 4.x has the leaked cfw which doesn't need gateway at all, only a NDS flashcard, 9.x may never get any cfw (except the gateway drm one...)
- 4.x can trigger the exploit via a NDS flashcard, 9.x can't do that, maybe you need 10 or 20 or however many steps to start the exploit
- 4.x can use gateway right out of the box, 9.x needs to wait 2 weeks or 2 months or 2 years