Totally disagree with OP.
Nintendo itself admitted they cant anymore effectively support two different platforms, thats why they merged their handheld and home console software divisions in one, and their hardware handheld and home console divisions in one. To be able to work much more effectively just on one platform.
With Switch there is no reason to continue with DS line or to release separate handheld platform because Switch is already both and gaves the great opportunity to release tons of different versions of Switch hardware.
Only reason why they still somehow suporting 3DS (if you look at current Nintendo 3DS games all are done by external teams), is beacuse 3DS is still selling good and it has low price point for market compared to Switch.
You can bet sometime at end of next year or in 2019. when 3DS dies, Nintendo will release Switch Mini, smaller Switch just for handheld play with price point of around $200 for start.







