In the Wii U fact sheet Nintendo supplied in connection with E3 2011 (and also CES 2012), it reads:
I wonder if this is the only output supported, or if Dolby Pro Logic II (five-channel) will be featured as well (for backwards compatibility reasons). I've seen no press releases or interviews detailing licensing of any Dolby technologies for Wii U.
While six-channel PCM certainly should cover a basic audio experience in most games, it's nothing new. PlayStation 3 and Xbox 360 have support for LPCM amongst other technologies such as Dolby Digital 5.1, Dolby TrueHD, Dolby Pro Logic IIz and DTS-HD Master Audio to name a few. I understand that Nintendo wants a somewhat cost-efficient system and perhaps theorizes PCM is sufficient to fulfil the demands of both developers and ultimate consumers, but I thought of how something like this would correlate to a certain thing Mr. Iwata said at the Corporate Management Policy Briefing/Third Quarter Financial Results Briefing for Fiscal Year Ending March 2012:
While he references graphic representations here in comparison to "the power games" and eventually that they do not hesitate to role out their resources, perhaps other aspects, such as physics and namely audio output, of a software title can be accounted for as well. It is not an area that is even remotely as popular as graphics, but by having support for a technology with which you can enable for example 16 channels (Dolby TrueHD), much atmosphere and ambience can be added to a game. Let's take Metroid or The Legend of Zelda series for an example; with these the player could experience very vivid environments where distant sounds of zoomers and keese respectively are heard. Even something as dripping water could add to the experience. PCM could certainly achieve this to some degree, but is it really enough for current expectations?
What Microsoft and Sony have in store for their respective next generation systems regarding the audio department should be less important than processing power and clock frequences when comparing the different systems. But if something like Dolby 3D or 22.2 surround sound (see NHK Science & Technology Research Laboratories) is implemented and marketed cleverly as a key selling point (not only for gaming), it could be tough for Nintendo to combat, at least only with PCM.
Sources:
Wii U fact sheet:
http://e3.nintendo.com/hw/#/about
Corporate Management Policy Briefing:
http://www.nintendo.co.jp/ir/en/library/events/120127qa/04.html