Yea obviously the Switch is the 3DS successor. Releasing another handheld system would cannibalize Switch sales and would hurt Nintendo.
The 3DS will continue to be the low cost portable option until the Switch drops in price a good amount. I think we'll see the new 2ds at $100 soon and the 3ds at $150 in order to keep them selling and allow room for the Switch to drop price next year to $250. I think at some point there will be a deluxe version of the Switch entering at $300, and a cheaper small version to replace the 3DS at a more normal handheld price once the 3DS finally dies off. Though I am really not sure how they would market a portable-only Switch since the whole name of the system is based on switching between portable and console. It'll be interesting to see what Nintendo comes out with.
By 2020 3DS will be on its last legs and Nintendo will probably introduce some sort of smaller cheaper version of the Switch to be at a more normal handheld-price.







