It's not going to fail. It still has the die-hard faithful who bought the Wii U and it should have all the people who still want a handheld gaming system (though that number will probably continue to shrink). It will have the Japanese handheld support that went to the 3DS and it might even have the support that went to the PSP/Vita, which was substantial (though Nintendo probably won't co-fund nearly as many games as Sony did).
The Switch will make money for Nintendo and it should have an install base near the range of the 3DS.
Now, that being said, the Switch is supposedly taking over for both handhelds and home consoles, so it needs to surpass the 3DS hardware totals and blow away the software totals or else it will represent contraction rather than growth.
