This is surprising, I figured Nintendo could easily milk this with another title. I guess there is the question of what they would do in the 3rd that they haven't done in the other 2.

This is interesting. Now to make Ian happy, why can't they apply this same principle to their other franchises?

They will want to save the series for the next platform, try not to kill it off now.

They're doing disruption, sequels don't work for that (Malstrom said Wii Sports won't see a real sequel for that reason either).

Brain Training is also a game with a purpose.  Utilitarian games can't get proper sequels unless a new use or an improved method becomes available.

People won't get a new Brain Training because they want more fun little games, they will get a new Brain Training game if they find some new ways to improve their thinking.  Right now Brain Training and the sequel, if people want a little more mental workout, are more then enough.