The gap is likely to be around 7.7m - 7.8m at the moment. With the launch of the PS4 in China and the XB1 returning to its original price, I think the gap will grow to around 8m - 8.1m by the end of January. Then you have February when The Order (with likely bundle) is released. I think the gap will be around 8.3m - 8.4m. But I think the biggest difference in sales will be in March when Souls fans get a chance to jump on Bloodborne, which is also likely to be bundled. The accumulation of momentum from January (China launch/XB1 price rise), the release of The Order and Bloodborne will see that figure rise to 9m by the end of March.
I'm not sure what games are releasing in Japan but I seem to remember a big game? I could be wrong. If there is then I think 9m is easily doable.
The PS5 Exists.