Too early to say yet. Definitely too early to be saying anything about the 3DS. The hardware sold very well for a launch, even if it wasn't an instant sell out, but the units of games sold during the same period were not quite as impressive (someone else can look it up but I think it was less than the number of hardware units sold). Ultimately, the mark of the 3DS' success will be in its ability to move software units.
Regarding Nintendo's next gen Wii successor; it's definitely too early to be prematurely calling another hit out of the ballpark. Lighting rarely strikes twice and Nintendo will have to come up with something special that captures the expanded audience once again enough to convince them that they need to replace their Wii.
As far as this generation goes, sure the Wii will close with the greatest number of units sold, but its marketshare on a month to month basis has done nothing but erode and there will be no rabbits pulled out of Nintendo's hat to reverse this trend.
The DS on the other hand, will likely go down as the best selling dedicated handheld gaming system of all time, if for no reason other than that the extended future of such devices is legitimately in question with the continued growth of iOS and Android mobile gaming.
