Just in case people don't know:
The 3DS is based on ARM11 which can be found in phones from 2006-2007
3DS has 128MB ram which comparable to phones from 2007
All that and yet it was Nintendo most expensive handheld to date was responsible for the company posting first loss ever. People looking at today phones and thinking Nintendo can match Moto G are expecting way too much if you ask me.
To be honest, 3DS conception happened before the smartphone boom, which is responsible for the ARM boom and the boost in performance of their chipset.
When 3DS was announced, ARM11 was just replaced by Cortex A8, which was the following of ARM11.
Between DS, which used ARM9 and 3DS, which used ARM11, you had 2 ARM CPU released: ARM11 et Cortex A8.
Between 3DS and next Nintendo handheld, you had 4 to 5 new generation ARM CPU:
Cortex A8, Cortax A9, Cortex A15, Cortex A57 and Cortex A72. And that's without talking about additional releases for mid tier devices, such as Cortex A7, Cortex A12, Cortex A17 and Cortex A53.
But again, I don't see any reasonable people asking for 1440p. I think it's similarly extreme to go with 480p. I think 720p is really a very happy medium and should be reasonably drivable by affordable mobile chipsets in late 2016.
At some point, a resolution that low will hamper Nintendo's ability to build lifestyle apps and such, which you know they will want to do.
I think they might want to consider scalability from a standard Android phone resolution so they can have developers easily port across their stuff.
To be fair, I see more gain for 480p over 1440p. Then again, 480p to 720p is twice more pixels to draw... which is questionnable for the gain in IQ for a 5 inch screen. But yes, 720p should be pretty much doable, the same way it's doable on Wii U. Although, I think 540p is a sweeter spot.
Then again, it's not only a price problem, but also a performance and bandwith one.
Just to put it simple: Tegra K1, in the Shield Tablet, runs Trine 2 at 1024x768 resolution, with a slightly worse framerate than PS360 version and slightly worse graphics.
We're talking about the most powerful SoC on the market right now.