I think this is where the famous warchest comes in and people wanting Nintendo to go third party now. At the moment they'd have enough to be sustained for a while to allow them to produce those AAA games for other systems and prove it could work (assuming it would work of course).
The comparison with SEGA comes up a lot but that was when SEGA had already failed. If Nintendo went third party now they would be in a much better position.
But yes, the shareholders are a whole other aspect of this that I hadnt thought about. You've got to feel though that whatever direction they take, the shareholders will be wanting a return and the Wii U at the moment is just as problematic.