The upcoming Konami title will likely be the first on the market to use the super-sized DS card.

Source: Konami Uses 4 Gigabit Cart For Visual Novel // Siliconera

Quote Originally Posted by Siliconera
As one of its selling points, Konami announced Tokimeki Memorial: Girlís Side 3rd Story is so big it needs the elusive four gigabit Nintendo DS cartridge. Konami says their game will be the first game in Nintendo DS history to use it.

Ni no Kuni from Dark Cloud developer Level 5 was the first game to announce the four gigabit cart. The official site still says it is on target for spring, However, Level 5 hasnít even made a murmur about it, which could mean the game was quietly delayed. Tokimeki Memorial: Girlís Side 3rd Story is slated for summer. Either way, companies will start rolling out four gigabit carts this year.
This will be intresting when people try to load this via SD Cards and there game/book is 512mb and all they have is a 2gb card..... ouch!!!!!!!!!!!!!!