The simple fact is, is that if Nintendo started to put their games on to the other two consoles, they would sell millions more copies of every game they put out. Take Mario Kart for instance, sold over 4 million on the Wii U. The current install base of over 30 million PS4s and Xbox, youd be looking at what, 5 million sales surely? Even more?
PREDICTIONS FOR END OF 2015: (Made Jan 1st 2015)
PS4 - 34M - XB1 - 21m - WII U -12M