It's funny, each time, i see a lot of people underestimating PS4 and each time, PS4 surprises them.
Most of us believed it couldnt reach 5M before February, back in december, it was insane, unthinkable, but it is hapenning just as planned.
Same thing will happen in Japan, if the majority think it's impossible to reach PS2 level of sales, PS4 will do the impossible, like always.
Predictions for end of 2014 HW sales:
PS4: 17m XB1: 10m WiiU: 10m Vita: 10m