Funny how that holiday spike keeps going higher, even though it's not always the same console... or even the same month to achieve that spike.
Holiday sales in general have been very strong this generation. While sales in the Jan.-Oct. period haven't been anything to write home about, aggressive Black Friday promotions have resulted in some of the most consistently strong holiday sales ever. The last two Q4s in the U.S. were ranked #4 & #5 among all fourth quarters on record, with same-gen console sales of 8283k in Q4 2017 and 8484k in Q4 2018. Of course, the Switch hasn't replicated the Wii's success, so we haven't gotten to the same level of sales we saw in Q4 of 2008, 2009, & 2010. If we focus on just PS & Xbox, the PS4 & XBO sold over 5M units every Q4 from 2015 to 2018, with a peak of 6.37M in Q4 2015, the best Q4 for combined PS & Xbox sales ever in the U.S. By comparison, combined PS3+360 sales only went above 5M in Q4 of 2010 & 2011, and combined PS2+OXbox sales only went above 5M in Q4 2002 (though it was a strong peak holiday quarter with over 6.32M sold).
Essentially, the holidays have cannibalized sales from the first ten months of the year, resulting in decent-but-not-great sales outside the holidays but outstanding sales during the holidays. November has also represented a much higher share of Q4 sales than in previous generations, though that trend did start late last generation after big Black Friday price cuts started to become common. I expect this to continue throughout next generation, which I think will follow a very similar sales curve to this one, though with the PS5/Scarlett split being closer assuming neither Sony nor MS make any major blunders.