Based on the data I've collected up through this past May, the PS4 was at 29,413k in the U.S. This means the PS4 sold at minimum 587k in the June-Aug. period, meaning a minimum weekly average of a bit over 45k. Last year, sales in the same period were 761k, or about 58.5k/week. This means the drop for the June-Aug. period was no more than 22.86%, comparable to the drop for the Feb.+March period (January was not down much for no obvious reason, while April and, to a lesser extent, May were down a lot because 2018 had God of War).
This also means the PS4 is so far at over 1.6M for the year, maybe a bit more, vs. 2082k for the Jan.-Aug. period of 2018. Assuming the average YoY drop remains about the same, the PS4 will sell 3.3-3.4M in the U.S. for 2019 as a whole.
Now only if we knew the exact numbers for each month. Unfortunately the one and only sales tracker in the U.S. has decided that information is off limits to the general public.