Nintendo are already third party, the quality argument is rubbish, will quality drop now that Nintendo have released its first of many mobile games ?
Quality will drop. It's a given. When I say quality, I mean the polish, the feel, the game play.
Look at any first party developer on any platform versus a third party developer on any platform. The quality is not anywhere near the same.
Mario versus any other platform game on a Nintendo console.
Uncharted, The Last of Us versus any other similar game on a Playstation platform.
Look what happened to Sonic. The games were pretty polished and felt higher quality when being exclusive to the Sega consoles. Now, they look, feel, and play like junk. Also, the appeal and desirability of everything Sega and Sonic is no where near what it was or could have been.
Even as a third party developer when Final Fantasy moved to multiple platforms the polish and quality dropped.
The polish and quality Nintendo gamers expect and are used to will drop.
Why would any of those things happen if they dont have a badly selling plastic box to go with their games?
Part of being a collector for anything is the strength, desirability of the brand and franchises that go with it. By being third party it dilutes their brand and products and no longer makes it as niche, exclusive, or I guess in collector/GAF/eBay vernacular, rare. It's not just the physical presence.