The DS family is great. Just like the Wii, the DS brought gaming devices to people who would normally not have considered touching a console while maintaining a moderate price and not going for highest possible technical specs. Interesting ideas: E-books on DS, learning software, a cookbook… Much of this stuff is now on phones – but overloaded with ads or pay for subscription service and often working only when connected to the internet. Sure, the first games heavily relied on touch input (even on games where it did not make sense… Zelda &§%!$) but by the time the 3DS came out, bad forced touch-controls were mostly gone. The 3DS made the lower screen a secondary screen and this is a nice thing. Having a map, inventory, counters… permanently visible, easily accessible and not clogging the main picture with loads of information.
The clamshell (not O2DS of course) design protecting the screens from scratches when carrying the console is a nice feature as well. Admittedly this design is prone to wearing down through normal usage and will require complex maintenance at some point.
Lastly, a personal thing: With the discontinuation of the 2|3DS line (technically they contain a GBA) the last gaming related remnant of my childhood/teenage is now gone. It felt awful… knowing the last thing that could be called a "Game Boy" is no longer in production.
So in theory: Yes. I would like an upgraded DS system (backwards compatible to DS(i) and 3DS). Higher resolution, better speakers, a capacitive touchscreen instead of the resistive one. And in reference to Moore's Law: It should be possible to offer a more powerful device now for a reasonable price. In practice nothing of this will ever happen. Gaming has shifted towards (even monthly paid) online play. "Time to move on! You're so 2008!".
Any newly released console (not only Nintendo) will be a DRM-infected *censored* focusing almost solely on online play (and banning any people gaining full control over their devices with the help of exploits). The console security has been improved (from the perspective of the manufacturers) more and more and a hypothetical "Super 3DS" would be no exception.
There are two kinds of consoles (handhelds and TV) nowadays: "Mega-DRM modern online consoles" and "Cheap retro-devices containing a few old games"
I will NOT move on. 3DS and Wii U are my last consoles. There are soooo many great games playable with those two – officially and unofficially.