In an interview on Kotaku, Itagaki said that Ninja Gaiden II might be the last in the series.

From the interview:

"Personally I think we were able to create the definitive 3D game in this series so I'm not planning on making any other games in the series," Itagaki said through a translator. "So I hope fans treat this as a swan song for the franchise."

When asked about a possible Playstation 3 version, Itagaki replied that "would be ridiculous" and expressed a desire to make something new, unrelated to anything else he has done, perhaps involving World War II.

Read the full interview over on Kotaku.

I don't know about you, but this depresses me. Ninja Gaiden is one of the few franchises I enjoy completely, and the thought of not having another one...I don't want to think about it.

And he's moving into WW2... great...

Nawww he said that that idea just occurred to him when talking to the interview. Nothings concrete. I don't mind him moving on!

Edit:
I guess this gen has a lot of the Old Giants moving on. The dinosaurs of the battlefield...

Hideo's done with MGS, or so he says.

Miyamoto seems to be piling on with non gamey things whilst directing other people to play around with his old ones.

There are plenty more... plenty of franchises too.

'This will be my last mission.'