The week 5 numbers are attrocious for the X1 perspectives in January.
The absolute rankings will improve for all systems (check the current hourlies), but the relative rankings still aren't very encouraging for the XBO's prospects this month. The COD bundle is far enough ahead of the Gears bundle and the Star Wars bundle close enough behind the Gears bundle for the PS4 to have been at a nearly 2:1 (if not over 2:1) advantage at Amazon for several days now, and for several days before that the PS4 had an unambiguous 2:1 lead. GameStop.com is telling the same story, with the PS4 at an over 2:1 lead as the XBO is barely registering while the top PS4 SKU is doing very well. At BestBuy.com it's not as lopsided, but with the COD bundle staying at #1 and the Gears bundle hovering around #13-14, the PS4 still likely has a comfortable lead.
While I don't think January's NPD will result in a roughly 2:1 win, it's certainly not inconceivable. The PS4 sold 92.2% more units than the XBO in January 2014, though at the time the XBO was still at $500. Last January the PS4 had a pretty big drop from the previous January, while the XBO grew slightly, but even then at $50 below parity for most of the month the XBO still was outsold by the PS4 by about 26.3%.
As it got a price cut to $350 back in October, the PS4 should rebound from where it was last January, maybe even pulling numbers close to Jan. '14. Meanwhile, the XBO might not grow as much. Granted, it was bumped back to $400 for 13 days last January, which hurt it a bit, but aside from that it was at at $350 through the entire remainder of the year (sans the Black Friday and Christmas sales). Here's the XBO's per-week averages through the first ten months of 2015:
There was a spike in February due to tax season, another spike in June due to the release of the new 1TB SKU, and another spike in October due to Halo 5. Take out those three months and January and you have an overall weekly average of about 47k per week. At most, the XBO will pull in the neighborhood of 200k. The PS4 staying at $400 for most of 2015 resulted in its sales through the first half of the year being overall flat from 2014, so we shouldn't expect any appreciable growth with the XBO either with it likely staying at $350 for the time being. Overall, I think the PS4 will beat the XBO by at least 30%, perhaps over 40%.
However, it's also possible that with the PS4 being at parity it will grow its overall market share at the expense of the XBO, and the XBO could shrink YoY, and the gap could grow to where the PS4 sells 50%, 60%, or possibly even 70% more units than the XBO this month. While January is usually a fairly boring month, I think it can provide some insight on how well the XBO can continue to sustain itself at $350, and what effects on market share the PS4 being reduced to $350 as well will have. This is the first time the PS4 and XBO have been at price parity outside the holidays for an entire month since October 2014, but this time the PS4 was the one with the most recent price cut.