No. I would say Wii was a blip on an otherwise downward trajectory. Millions of people bought their first and last console, and a few millions bought Wii then either PS3, or more likely X360+Kinect.
Wii U launches and we're back to GC level sales, which is basically the core Nintendo audience who will stick by Nintendo through thick and thin. At this stage I think Wii U is more or less guaranteed to sell as well as GC, and prhaps, because at least some first timers who bought Wii will have a second go 'round Wii U might sell slightly more.
The only thing Wii failed to do is secure a substantially increased multi-generation fanbase. But it did not do long term damage to the brand. The only thing that puzzles me is why the vocal core Nintendo fanbase didn't see that and assumed they'd have multi-generation dominance when the top 50 games for Wii was dominated by party/casual games, with a smattering of Nintendo stock franchises from previous generations and a couple of Lego games. The only "non-casual / party" new IP appearing in the top 50 are below the top 30. And worse still, Nintendo didn't recognise this as a sign of the one generation wonder phenomenon. Or perhaps they did but they really had no clue about how to deal with it.
PS4 and 360 on the other hand is completely dominated in the top 50 by the sort of IP that long time gamers play, or that people new to gaming play if they've found themselves a new hobby that will last them for years to come. And plenty of new IP in their top 50s, including in their top 20, that are non-casual/party.
The trick is to market aggressively to the core long term gamer but also give casuals a reason to buy your console. Nintendo just has the balance all wrong for a long term strategy.
“The fundamental cause of the trouble is that in the modern world the stupid are cocksure while the intelligent are full of doubt.” - Bertrand Russell
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