For me, much more interesting than 'what could have been?' is 'why did they let this happen?'.
Assuming, as many seem to be, that there were many things which could have been done to retain the high sales of early 2008 and before, why weren't they done?
Possibilities:
-Nintendo is unable to create as much software of the quality it wants to in reasonable time frames. This perhaps led Iwata to say about how they were currently in a phase of 'lessening consumer expectations' because sustaining the previous excitement was simply not possible.
-Nintendo is working hard on something new, and sustaining what's out there with minimal support.
-Nintendo staff have been consumed with DS games, Wii Channels/Wii no ma TV station, etc which are given the same sort of development love as their games.
-Nintendo has not checked its sales figures for the last 18 months.
-Nintendo enjoys making games without the weight of stockholder expectation on their heads, and is trying to get rid of them!
This is an extreme interpretation of 'lessening consumer expectations', as meaning 'leave us alone with your demands for more stuff!'.