Extra Easy Prediction: The PS4 won't be the eighth gen console with the best post-successor sales

[src]

Lets see:

WiiU had non existent sales during its lifetime, let alone after it.
XB1 has effectively stopped selling in its last year of its lifetime, let alone after it.

PS4 is the default winner here.

It will probably do 10-15 million post PS5 (latter if Sony decides for a price cut).