I agree, but only because DS's first holiday is a poor example. The problem with looking at early DS sales is that Nintendo's software strategy was radically different. Once Nintendo got their ducks in a row, the system took off and sales trends were like night and day. 3DS is doing well, and it's possible Nintendo may be able to get it on the DS/Wii track, but they're not there yet.
If you've followed Nintendo earnings threads, Nintendo almost never makes predictions they're not sure they can bear. They're very different than Sony and Microsoft in that way. 16 million is a big number, and it would be great for the first year, but Iwata would not have told their shareholders that 3DS would hit that mark unless he was confident that it could do even better.
It's really said that you can't have a luke warm appraisal of the 3DS without people pulling out the "3DS is doomed" strawman. It's impossible to have a rational sales discussion if people can't be even slightly bearish on a console that regularly misses sales targets.