I'm posting this because people keep expressing surprise at the drop in sales when the exact same thing happened with the DS. Let's compare 2007 to 2008 DS for the same week.
Media Create Week 7, 2007: NDS - 136,999
Media Create Week 7, 2008: NDS - 62,362
Like 3DS, DS had two monster years previously and 2008 marked the year where it would hit saturation point (though, DS was of course doing it at a consistently higher level than 3DS) aka settling for 'normal' sales - I think that's the same thing happening with the 3DS here. A drop was inevitable. The kind of sales the 3DS put out the last couple of years are not normal for any hardware to consistently do YoY, for example, 2012 3DS >>>>> any post-2007 year for the DS in Japan. I think a new model isn't the solution because 3DS will never reach those heights, more importantly, I think a strong software schedule is what's needed and that's what kept the DS afloat for years though the market is also a little different now and 3DS doesn't quite have the consistent level of support the DS enjoyed.