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

[Dr.Vita]

Mnementh said:

Dr.Vita said:
NX was already teased, Wii U will be dead in 1-2 years imo.  

If NX is the successor to the WiiU, will Nintendo never replace the 3DS? I think assuming the NX is the 4DS is a safe bet.

Or a fusion of both.