Hmmm... I don't think it needs to go as low as $199. I mean, if you take a closer look at the charts for the last two or three months (Since Windwaker release to be more precise) you will see that the Wii U is the console that has had a more steady growth week after week. Sure, it's a growth that doesn't get noticed much because the initial baseline was too low (20K) but it's a growth nonetheless.
I truly believe that with a $250 price tag, sales should stabilize somewhere around the 130K per week. Which should keep the console safe until the PS360 dissapears from the market and the Wii U becomes the only option available on that price range.