I do think it will appear to be an incremental upgrade to the DS, unless they do something drastic with packaging. You're average Mom will go into a Wal-Mart that Uncle Bob doesn't work at and inquire about the difference between the 200-250 dollar 3DS and the 150 dollar DSi. The Wal-Mart clerk will then say "Well that one has 3D." The mom could then very well say "That aint worth 100 dollars."
**fast forward 12 months**
Kid: "Mommy, mommy, I want *this* game!"
Mom: ::looks at game:: "Only for Nintendo 3DS... wtf?!?"
**meanwhile, at Nintendo HQ**
Reggie: "Ha-ha! Now, little Timmy's mom bought two DSes when she could have bought one. My evil plan is working perfectly!"