The Nintendo 3DS will continue to be produced post launch of the Nintendo Switch. Nintendo President Tatsumi Kimishima confirmed as much to Bloomberg saying that the handheld console still has growing users and momentum...
"Thanks to our software, the 3DS hardware is still growing. So that business still has momentum. And certainly rather than being cannibalized by the Switch, we think the 3DS can continue in its own form."
I'm not shocked by the news, as it seemed a silly notion that the 3DS would somehow disappear in the Switch launch. There is still plenty of enjoyment left to be had in the console, although now that the system is entering year 5 of it's lifetime...you'd have to think Nintendo is looking into the feature.
The DS, which is the most successful handheld console of all time, was switched out for the 3DS after 7 years. One would have to imagine there are already people plotting and developing concepts for what's next for the handheld market for Nintendo. I'm not sure how they could follow up the 3DS, but I'm sure they'll find a way!