I - Bring on the competition. I have yet to see anything from Sony or MS that makes me think they are capable of using their motion controls to dethrone Nintendo
II - We have three gaming options that are cutting local multiplayer to save costs and allow for online multiplayer, and one option that is focusing on local multiplayer at the expense of online. Who's overfishing a market now? Also, Nintendo made vast improvements in their online from GC -> Wii - inbuilt wifi, many online non gaming functions and some strong online multiplayer games like Mario Kart. Next generation will be even better.
III -
See 3DS launch lineup
Cry
Be first in line to buy a 3DS
...
Profit
IV - last I checked the Wii's attach ratio was ever so slightly higher than the PS3's, and moderately close to the 360's. The DS's is extremely high for a portable.
V - the same can be said for Sony, MS, and pretty much every large 3rd party developer.
VI - You could be right, and next generation is certainly shaping up to be as interesting as this one was. Next generation Nintendo have the disadvantage of more competition, as you said. Both due to competitors having motion controls and also because Sony will not cock up the PS4 launch as much as they did the PS3's.
However, Nintendo is in a better financial situation than they were a generation ago, and they have a much stronger base to launch their next console - the Wii has the Gamecube beat in pretty much every aspect (except number of games entitled Eternal Darkness or F-Zero)
