It will sell well.
Plenty of people will upgrade for the improved loading and other conveniences, and many 3DSs have aged quite a bit over time and with use and could likely use a refresh. My own 3DS XL has been has a very obvious screen tear (from my dropping it) along the top screen from time to time. I'm not going to go out and buy a new 3DS XL for a marginal problem but I will buy a n3DS (I think I will downsize to the regular, XL is too big for on the go for me) to fix said problem AND get a much better user experience.