Why is so hard for Wii U sell 20,000,000?

[Ryng]

Danman27 said:
the wiiU has sold 500K in the first three months, I don't see how that translates to 4 million this year. The wiiU is going to be dead after next year.

Last year Wii U sold in 13 week 501,000. +3,600,000 in 2014

This year Wii U sold in 12 week 507,000. +4,000,000 is very possible.