Actually even with a staggered launch over 5 weeks (3 weeks in japan and before launching in europe at all) the original DS sold nearly 3 million. The first week in the US alone saw 230,000 sold. The DSi launch saw 435,000 sold in the US in the first week, 92,000 in EU in its first week and 170,000 in Japan on launch week. We can talk legs all you want but based sheerly on numbers its the weakest console launch in nearly a decade...even the GBA Micro sold more than double, to put it in perspective it barely beat the launch of the Neo-Geo pocket color which launched online only.
Why would nintendo feel the need to follow in anyones footsteps? Nintendo has been taking baby steps and laughing all the way to the bank, the DS launched as an "side project" and took off quickly, yet it retained full backwards compatability with the GBA, the lite was simply a redesign with no real internal changes at all, and finally the DSi launched dropping the gba slot long after the gba was no longer supported while adding an sd slot, browser, cameras, etc leading to their online strategy. Thats the kind of transition I was talking about...IMHO Sony's strategy is a horrible misstep.
Don't forget the DS Lite, which had massive sales performance. Perhaps the best redesign launch ever. It was sold out for how long?
Anyone can guess. It takes no effort to throw out lots of predictions and have some of them be correct. You are not and wiser or better for having your guesses be right. Even a blind man can hit the bullseye.