At 175K without any obvious mega hits (unless I'm forgetting something?) coming until Fall, I feel that's not a good sign for momentum, at least for the first eight months.
Obviously it isn't dire, but it isn't exactly a major hit device at that point, at least currently.
Well, the fact it isn't the main choice is obvious, we aren't seeing what's happening now in Japan. But it's something normal IMHO: US is slow in adopting new hardwares. In fact, DS had its best Christmas not in 2006, with Lite already launched, but in 2009. It's just a matter of time and lineup increasing and increasing. If the lineup continues increasing with big sellers and many other titles, we'll see the platform rise.
Moreover
There's a name for a giant drop after December: January. For reference, DS's December->January drops:
-80%
-85%
-85%
-90%
-83%
-87%
And I'm lacking last year's numbers.