I can see it happening if they go for a unified design. It would have to be a memory card type that fits on both. Preferably similar to 3DS and DS cards so that both consoles can be backwards compatible. WiiU gamepads would be paired with the home console (and sold seperately) to enable DS and 3DS game compatibility. IMO, the disc drive would be a must. Having backwards compatibility with WiiU and Wii software will require it (can't just rely on digital format), though no new games will be made in disc format. But all this implies perhaps a complicated hardware design since it would need the DS, 3DS, Wii and WiiU processors on board for hardware emulation on top of the new chip.
Back OT, one potential issue would be the storage size of the memory card cartridges. Too much and too fast would be expensive to make. We might underestimate the capacity needed to have games run at native 1080p or higher resolution. And read speed since the data would be very large.
e=mc^2
Gaming on: PS4 Pro, Switch, SNES Mini, Wii U, PC (i5-7400, GTX 1060)
