I would certainly like to see a Switch-compatible dedicated handheld platform, preferably one with dual screens and 3DS/DS backwards compatibility. The Switch is already built on mobile technology. There’s no reason they couldn’t fit that technology into a more pocket-friendly form factor, and make it the latest in their DS line along with that.
A cheaper, portable-only Switch would also fill in the more budget-minded gamer niche currently occupied by 3DS systems rather nicely. I think the mobile market, including the portable gaming market, has certainly proved that there is a demand for different screen sizes and form factors.
This way, Nintendo continues their successful DS line, without needing to significantly split their software support between two platforms, since the majority of titles could be cross-compatible.