The GameCube was released in a pretty different time though.
Development costs were a lot smaller and the hardware was cheaper. Microsoft being a newcomer was also less entrenched in the market. Japanese games still sold pretty well in the West and there was no iOS/Android to have to worry about either.
GBA was selling at a higher rate per year than the 3DS is and the early 2000s were the peak of the Pokemon licensing craze (major movie releases, tons of merchandise, etc.) which helped buoy profits. Even so the GameCube fell horribly short of Nintendo's target for the system which was 50 million units.
What is the next console supposed to be anyway? Just something slightly "better" than a PS4 released 4 years late starting with a library of 5-7 games versus like 400+ (by that time) for the PS4/X1? There's only going to be a market of about 14-15 mill Nintendo die hards for such a platform and third parties won't touch it, the Wii U is basically the official divorce between Nintendo and third parties. You can't make money off a platform with such a low userbase and such high development costs.
If it's a "Fusion" device than most likely it's just the handheld chip, maybe "super powered" a bit and thrown into a Apple TV/Vita TV style casing, but that's really just a way to play portable games on your TV. But that should be gravy profit for Nintendo, just like the iPod Touch is basically just another version of the iPhone, it doesn't sell a ton for Apple, but it's a bonus and fills a market need.
