The Wii U (if memory serves) is tracking below the Gamecube, but it also started at a much higher cost. I think the recent sales bump in Japan shows there is decent demand for it if there are appealing games being released. On the other hand, Nintendo has a habit of prematurely dropping their consoles, and I can't see their first party support lasting much beyond 2016. And third party support won't pick up the slack. I believe it will sell less than the N64 but more than the Gamecube.
About: 25 million
The 3DS, while it will likely be the first or second best selling system of the gen, lacks the casual games that made the DS such a breakout success. It's far more similar to the GBA, which had traditional Nintendo series such as Pokemon and Mario but didn't expand beyond the traditional Nintendo handheld audience. If Nintendo continues with their current strategy, I see the 3DS ending its lifetime between the GBA and DS, likely close to what the original Gameboy sold.
About: 120 million
