Japan was always strongest single market in gaming (if we dont count Xbox) after US and after hole Europe, there is reason why people are comparing US, Europe and Japan sales.
Japan always had much bigger sales compared to any European country, so difrence betwine PS4 Japan numbers and Germany and UK number are actualy very low, for isntance PS3 sold more 4-4.5m consoles in Japan compared to UK, while with PS4 difrence is only 1m curently and that difrence can easily become smaller.
PS4 sales in Japan compared to rest of world PS4 sales are definitely lowest compared to previous Sony consoles, including PS3. PS3 Japan sales were around 12% of world wide PS3 sales, PS4 Japan sales are curently around 8% of world wide PS4 sales and that perceant can easily go even lower.
So yes, Japan is becoming less relevant for Sony, PS4 sales everywhere outside Japan are amazing and Sony know that Switch will own Japan in any case, so I think they are not worry at all about Japan market beacuse they know they will have great sale reagardles Japan market.
