From fiscal year 1991 to 2006, Nintendo sold about 300 million units of hardware, 1.5 billion units of software and posted posted profits of about 15 billion.
So during the 4th/5th/6th generations, Nintendo was averaging about 20 million units of hardware, 100 million units of software and 1 billion dollars in profits annually.
Nintendo made some pretty big mistakes this generation that cause them to miss out on those types of numbers.
Highest priced Nintendo generation ever, adjusted for inflation u could get both Nintendo handheld & console for about $300 in 1993/1998/2003 vs $500 in 2014/2015.
Nintendo sold hardware at a loss for 3 consecutive years, 3DS for a year after first price cut & Wii U for 2 years post-launch.
Customer confusion, many people think or thought 3DS was just a DS revision and that Wii U was just a Wii accessory.
With more affordable hardware, sold at a profit along with strong advertising/marketing, I think Nintendo can certainly get back to their 100 million hardware, 500 million software, $5 billion profits per generation that they had back in the 4th/5th/6th gen. If they can do that then there is absolutely no reason for Nintendo to go 3rd party.
When the herd loses its way, the shepard must kill the bull that leads them astray.