i seriously doubt that, if they r not interested in GC online, then a handheld shouldn't be an option.
From the comprehensive Nintendo DS examination, found on IGN.com.
IGN said:
Wireless network play is a huge obvious considering that the company has been giving away Wireless Adapters for the GBA in specially supported games (namely Pokemon: Fire Red and Leaf Green), showing just how capable and cheap the technology is. Nintendo is pretty set in offering wireless play for its system ever since it launched the Wave Bird for the GameCube, and in the case of Project Nitro, we've been told that the system will be capable of supporting as many as 16 players in a network via its own proprietary format. And most likely using the same wireless technology used in the Game Boy Advance adapters.