I will only buy the Wii U when it is at or under $199 and in its second or third year on the market with the start of a growing library of games.
Wii launched at $249 in NA and that was an attractive price that ultimately lead to the Wii winning the current console generation.
With the Wii U launching late 2012, it will hopefully gain support from third party developers critical for its success against its competitors: Sony and Nintendo. Touch controls, improved GPU/CPU, HD graphics, multimedia streaming/synchronisation and an improved online system will be features of the Wii U. Hopefully full backwards compatibility with the Wii that will automatically increase the library of the Wii U at its launch.