I think people are misunderstanding Iwata when he said a single game can turn things around.
You gotta start somewhere and that start is usually with a single game. It's what you do afterwards to keep that momentum going that confirms that turn around.
He doesn't mean you release one game that sells consoles and then sit on your ass.
So yes, ONE GAME can turn things around if you build on it. If Nintendo does or not remains to be seen.
Nintendo should be dropping bombs every couple months from here on through the rest of the year but that's easier said than done.
What disappointed me was that Nintendo didn't capitalise on the small boost that Zelda WWHD gave the console last year. Five small boosts are as good as one big one. Maybe it would have worked, maybe not, but at least try. It doesn't cost that much.