I think almost no other console took longer to reach the first million in Japan than the PS4, so the machine has definitly recovered nicely here.
The fact it reached 5 million just before PS3 is always a good sign and the PS4 continue to be up YoY. The last home console, the Wii U, died before 4M, despite being from the most beloved firm in Japan.
Western games are doing more and more good numbers in Japan, but let's hope the japanese studios will be able to bring more important games like DQXI, Monster Hunter World and Kingdom Hearts III, allowing the machine to reach 10M.
The Switch will have all the million sellers it wants in Japan (Zelda, Mario, Splatoon, Fire Emblem, Pokémon, Animal Crossing...), so unless people want a market with only one platform holder, the PS4 has to be supported.