I'm not worried about them at all, sure they are secretive about the Wii U's real hardware and their rumored games but time and time again Nintendo may be down, but not out. Sure the PS4 is powerful console, but that doesn't mean it automatically wins because of the graphics, last gen PS3 was the most powerful but had alot of flaws, right now Sony is in a really tough situation, this system might make or break them really hard. They are losing alot of money, getting rid of companies and buildings that did not break the 50k selling point.
On that day, Sony lost their stock by 2% or 20% and Nintendo gained at the same time, why? Because everybody is on the fence about the price and worried that Sony might pull off a "599 US DOLLARS!" like they did at E3. Now with people getting laid off by the days and weeks with barely any money for themselves, It does not look so good for Sony's price point like they did with the Vita's $250 price tag. The Wii U has been out for 4 or 5 months and already fanboys are celebrating the 'death' of Nintendo because of the graphics. The xbox 360 when it first launched is almost up to par with the PS2's graphics and look at it now, over time devs might be able to have greater graphical textures like Super Mario Bros to Super Mario Bros 3.
Also about the 4% of developers, there were developers from EA developing for the Wii U, saying that is runs 'beautifully on Wii U.' Crytek were developing Crysis 3 for the Wii U, it was almost done and ready to announce its pre order and another game was about to be announced exclusively for Wii U, EA canceled it simply because they are 'butthurt' at Nintendo's decision about saying no to this deal with Origin taking over their online services. Now a big company like EA not supporting the Wii U might cause alot of developers saying "Well if EA isn't developing and saying its not a next gen console then I wouldn't risk it."
Like i said, Nintendo may be down, but not out, they pulled it off with the Wii and its their highest selling console ever because of their ridiculously low price. So if Sony blows it with their price decisions, I don't think they would be around anymore.