Ninja Gaiden: Dragon Sword was based on input from an exclusive focus group: his own children.
"We're doing a lot of research, that's about all I can say right now. Although, to add on that note, my kids have been saying they want a game for the Wii. To tell you the truth, Ninja Gaiden: Dragon Sword, that's because my kids were asking for one of my titles to be on the DS."
We already know that Itagaki's been thinking about Wii games, as has Ninja Gaiden Sigma's Yusuke Hayashi, so this is just further reinforcement of the possibility. Itagaki's kids must have some skillz if Ninja Gaiden games are being designed for them. The good news is that, if Team Ninja is designing what appears to be a real action game in response to these kids, there's a good chance that the Wii game will be similarly hardcore.