Since the last mainline Final Fantasy to see exclusive release on a Nintendo machine way back in the days of the Super NES, and the subsequent falling out between then-Squaresoft and the Big N's insistence on Cartridge over CD, there has not been another numbered entry of the series developed on a Nintendo Home Console since.
If GamesMaster UK's sources are to believed though, that could change quite soon.
According to the site, Final Fantasy XV has been in full development since January 2010, not long after XIII's release, and including concepts and pre-production planning it was two years before that also.
Currently the development team number stands at around 200 people, and Square-Enix are aiming to have the game hit all 'current gen platforms'; whether this would mean Machine Release Timespan (Wii) or Power Level (Wii U) is unclear, though this definitely puts one of them in the running, and Square are certainly more comfortable with releasing huge RPG projects on Nintendo machines in recent years with the Dragon Quest games as proof positive.
Aside from that, the title certainly sounds ambitious, with the game looking to have an overall design and battle system highly evolved over that of Final Fantasy XII, with the ability to target individual body parts in fights, and an open world environment and sprawling cities like in the Assassin's Creed games.
In fact, Square's head-honcho Yoichi Wada wants the game's scale to outclass Elder Scrolls V Skyrim, and for it to surpass FFVII in sales and recognition. The game's director is reported to be the same guy who directed FFs VI, IX and XII, Hiroyuki Ito.