I think the extra screen is a gimmick that won't fare so well. The Wii U will just be a faster Wii with 1080p output. That is probably enough though. It will have the same screen resolution as the PS3/360 and likely be faster. That means on release it will be the most powerful console on the market.
Nintendo doesn't have to worry about the next Sony/MS consoles because when the other two decide to release a new console, Nintendo will be in a position to well yet another console. There is a lot of wisdom in Nintendo's choice to not double the price for a 10% improvement in system power since a few years later you can spend the remaining about you saved by not buying their competitor's system to buy Nintendo's next system and come out ahead for the same price.
As for the touch screen. The fact that only one touch screen can be used at a time will dramatically limit it's usability.
