A Nintendo phone with Android wouldn't be Nintendo's new platform, it would be Nintendo hardware running Google's existing Android platform.
Nintendo develops their own platforms to run with their own hardware, always.
In addition, Google Android is fairly low down on the foodchain when it comes to software development. Currently it goes:
Console and handheld - These are on an entirely different level. You go from discussing contracts of a few tens of thousands or hundreds of thousands, to in the millions. It is a whole other level from any Smartphone or mobile platform. DS titles, for example, are treated with much more weight than any iPhone or mobile projects; it is the equivalent of the weight in building and finishing a nice house in comparison to building a 1 car garage or a shed. The DS project is worth MUCH more than any Smartphone or mobile project ever could be worth.
As far as the priority chain for Smartphone and Mobile, it is not changing anytime soon, and currently goes:
iPhone - soon there will be 100 million devices running with one platform (very soon, 33 million sold in the last 6 months), one set of assets required (since all of them have the same screen sizes), and one version of the game required (since flags can be used to slow down software on higher end devices). This is a good place to sell applications, and also showcase software for nice contracts for development on other platforms.
J2ME - established, and most widespread, already hundreds of millions of phones running with it. The major issue is that due to hardware differences, many different versions need to be made.
BREW - Over 100 million BREW customers in the US. This is a gigantic portion of current CDMA phone customers (Verizon for example). This is third because many BREW devices are versions of J2ME devices (ie. Motorola RAZR2 V9 on J2ME and the V9m on BREW).
Winmo, Blackberry, Android are typically seen as optional platforms that very few take very seriously. Essentially, the market is crap for software on these, plus they're more expensive to develop for than the above platforms.
I describe myself as a little dose of toxic masculinity.