Whilst I fully agree that even considering the console for this version would seem odd (even case scenarios for Nintendo would have estimates for sale after 2 years less than 20 million), 50 million seems a pretty high standard to set considering that the Xbone, to my understanding, is no where near that figure, and no console in this generation has sold 50 million units solely in the West.
I hear that the Switch isn't too hard to develop for though, development kits are quite cheap, and since it's replacing both the Wii U and 3DS, you'd think that it would sell quite well. If you want to get ahead of the game, I'd recommend looking into it when the next major Pokémon game is announced for it.