Final Fantasy XI Producer Hiromichi Tanaka presented a keynote about future Square-Enix Massively Multiplayer Online (MMO) games at the Game Developers Conference in Austin, Texas today. Tanaka stated that the Wii is not a platform being considered for MMOs at this time.
"As for Nintendo Wii, it will be pretty difficult if you were to cross-platform for a couple reasons," Tanaka responded when asked about the possibility of a cross-platform MMO appearing on the console. "One is that Nintendo's currently not allowing different cross-platform titles, and as you know, the resolution differences make it harder for us to make cross-platform games. Currently we're not looking at Nintendo Wii as a platform."
Tanaka did state that an MMO on Wii is technically possible so long as the console receives a hard drive attachment. Nintendo has made no statements about producing such a device for Wii.
The only true MMO to appear on a Nintendo platform thus far is the GameCube title Homeland. The game was created by developer Chunsoft and saw a limited release in Japan back in March 2005. The other server-based online RPGs for GameCube allowed up to four players in the Phantasy Star Online franchise, costing approximately 10 USD per month for a Hunter's License.