GB: 118.60 million
GBA: 81.51 million
DS: 153.99 million
3DS: 43.33 million
Obviously you would expect the sales to be lower on the 3DS considering it's only about halfway through its life, but at this rate, by the end of its life, it's not going to do any better than the GBA, which is lower than usual. It'll probably even do worse than the GBA unless they pull some kind of miracle lineup next year, since sales tend to slow down as time goes on. Even Nintendo themselves have commented that while they're happy with where the 3DS is now, they expected it to do better.
At any rate, my point was that on the whole, Nintendo is not happy with how this generation has played out. The 3DS is doing well, but worse than they expected. And the Wii U is absolutely struggling to gain relevance, and so far is Nintendo's worst selling console ever (not including the Virtual Boy). Nintendo is probably more than happy to move on as soon as realistically possible.