Game & Watch-43 million (1980-1990)
Gameboy-54 million (1989-1996)
Gameboy-64 million (1997-2003)
GB Advance-81 million (2001-2008)
Nintendo DS-154 million (2004-2013)
3DS-50 million and rising (2011-2014)
3DS is on track to sell around 70 million, give or take, which is higher than the average Nintendo generation when excluding Nintendo DS.
Will next-gen decline? Maybe, phones/tablets do offer up added competition but at the same time people are quick to point out mistakes Nintendo has made with 3DS so could a big part of that decline be due to Nintendo's choices and not necessarily because of the competitors? I personally feel it's a mix of both.
Either way, it's pretty hard to same that the handheld market isn't still healthy, depending on the decisions Nintendo makes with their next handheld, it could either decline, rise or stay stagnant, I would predict anywhere from 50-80 million lifetime.
When the herd loses its way, the shepard must kill the bull that leads them astray.
