Every other developer basically always has a main series game for each franchise underway. Fans have never been in any doubt that Halo 2,3,4,5 or Assassins Creed 2,3,4 or Killzone 2,3,4 has been underway, In Nintendo's case they drop games for years at a time, or they come back in a completely different form.
What I'd like more than short dev times is an understanding that if Game X was successful, Game X+1 that is VERY similar is in development. For example: Galaxy 3, Wii Sports 3, Paper Mario 4, Luigi's Mansion 3 should unquestionable be in development. Yet there is a huge question mark over whether they are. 3D World, Wii Party and Mario&Luigi are no substitutes just as Assassins Creed Modern Warfare wouldn't be an acceptable AC sequel.
It's one thing third parties have right, by virtue of them seeking to extract all possible value from a franchise. Nintendo doesn't (or they somehow think retro re-releases count).