Here's the thing: Nintendo had to be conservative with the Wii, or else it would have been very risky.
I just want to interject and point out that being too excessively conservative is also taking a risk of sorts. I don't think this will happen with the Wii U, but if Nintendo had really cheaped out on the hardware and made only the bare minimum of updates in order to pull off the new controller gimmick and HD there would have been a strong possibility both the market and developers would have wanted nothing to do with it.
Again, I don't think that's the case because from the rumors we are hearing it seems like at least most developers are pleased with it. But it was something Nintendo could have done.
Maybe the best example I can think of where a console went too conservative and ended up failing as a result is the Atari 5200 which was the sequel to the far more popular Atari 2600. The 5200 was an extremely minor and insignificant improvement over the 2600, so the market rejected it. It was just too similar to the console that came out before.
Then Atari made the same mistake all over again by following the 5200 up with the 7800 which was yet again another minor incremental improvement over its predecessor.
One thing Nintendo has shown with the Wii is that the market will be willing to tolerate an incremental hardware improvement, so long as there is some major gimmick or other selling point to go with it. In the case of the Wii there was of course the motion controls, and as a result of that people were able to accept that it was just a Gamecube on steroids. But the Atari 5200 and 7800 didn't have anything like that. Same basic controls and same basic software, with just minor graphical improvements.
Was going conservative with the Wii hardware a risky move on the part of Nintendo? Well, if the motion gaming aspect wasn't there the whole thing would have flopped. So I think Nintendo was taking somewhat of a gamble, albeit a very educated one.