Here is what i think:
First, i'm pretty sure the NX will not be a sucessor to the 3DS and Wii U. Either a smart phone, or a streaming device.
For a sucessful next-gen console, their only one chance wich is to launch at the same time as the PS5/X2 with similar power and architecture. Mid-generation systems never work. Yes, this means biting the bullet with the Wii U until then... but wait!
For the next portable they should have a system with the same architecture and power as the Wii U. Games made for one could be made available for the other. This would extend the life of the Wii U as the home console disc based variant and the new portable would come off the gate with a solid library of games. Not to mention that the development time for new titles would be shortened because many tools are already developed.
That would be my master plan to get Nintendo to be in the race once again (in a broad way). Changes have to be made in other levels to ensure all systems are in competitive grounds.
If after this the Next generation home console failed to get at least 1/3 of the market then they should give up completely and just make systems for the casuals... aka Wii 2 with better motion controls, etc.
