“I now regret that we didn’t tie up with someone outside the company to market the Wii. If we had done that, the fate of the Wii might have been different. Now I am aware that we should not rely too much on ourselves. You will see what I mean by this when we market the 3DS and the Wii in the future.” - Satoru Iwata
It seems like Iwata is referring to teaming with third parties for more content instead of relying so heavily on first-party games. Even with Nintendo pumping out first party content, they can’t expect to have a full slate of content that will keep consumers interested and busy for the entire lifespan of a system.
Then again, Iwata may be referring to something other than third party developers with his statement. The wording leaves it open to interpretation.