Some persective- the DS during its heights (Holiday's 07 and 08) was selling over 1 million per week starting in mid Nov, and went over 2 million in a single 2-3 times.
Then again we may never quite see something like the DS again (the pure casuals are content with their Ipads/Phones/Touches and will not buy a DS just from Brain Age, etc this time around, I think the 3DS will resemble GBA in library...more core centric, good remakes, the GBA had NES and SNES remakes the 3DS will be loaded with 5th and maybe 6th gen remakes), and it will do a bit better in sales mainly because it is coming off the heals of the DS.
I think the 3DS will have a better library than the DS, but will end up with around 100 million in sales. Maybe more of there is like 5 version like what happened with the DS (I owned a DS phat, DS Lite, and DSi XL)
End of 2009 Predictions (Set, January 1st 2009)
Wii- 72 million 3rd Year Peak, better slate of releases
360- 37 million Should trend down slightly after 3rd year peak
PS3- 29 million Sales should pick up next year, 3rd year peak and price cut
