Total Lead: 276,716 – PS4
PlayStation 4 Total Sales: 8,748,755
PlayStation 3 Total Sales: 8,472,039
The big discounts and promotions for PS4 helped it out in December, but this should still be a close race with PS4 sales plummeting back to sub-10k per week by now.
This won't be a close race. The PS3 sold 420k units in the upcoming three months of the comparison (month 72-74) while the PS4 will do about 150k in the same timeframe. That will eradicate the current gap and make it hover around 0 in three months time and the PS3 will build its lead from there.
In the following twelve months the PS3 sold 880k (entirety of 2013). The comparable timeframe for the PS4 stretches from April 2020 to March 2021. The PS5 is expected to launch during the later months of that period which isn't going to help the PS4.
Alternatively, you can project yearly PS4 sales from here on out. The PS4 sold close to 1.2m in 2019. ~700k in 2020, ~300k in 2021, ~50k in 2022. Even if you bump those yearly projections by 100k each, you'd still only arrive at lifetime sales of 10.1m units. The PS3 finished at 10.47m.
It looks like it's a foregone conclusion that the PS4 won't reach PS3 numbers, so the next best goal for the PS4 is to reach the 10m mark.