As expected, Sony did indeed overshipped last quarter to reach that milestone. Going from 15'0M to 13'5M is a huge drop. It seems Sony won't produce too much deals this holiday season either. So PS4 should end the year selling 14'5M to consumers by the end of the year and then a huge drop during Jan-March 2020 compared to 2019. This seems to be due to TLOU 2 being pushed back to May. Despite all of this, software numbers remains super impressive and total profits are even higher than a year before, so good news for Playstation brand.
People pay too much attention to hardware total sales...To me is even more important the amount of software sales you have. That represents better how really important is the console to consumers and developers, and Sony have the 4 best selling software consoles of all time, including handhelds. That's why trying to give lessons to Sony about tactics they should do about exclusives, 1st party portofolio, adquisitions, ... it's just super ....."unnecessary" to be polite. They're the best doing this thing, by far, and they have been the best since the last 25 years. They'll do fine with PS5....
PS4 now will enter the farewell season of its life. It seems Sony doesn't care about discounts so probably won't see any even until PS5 launch. The console will still sell/ship around 115M by the time PS5 launches, at least, and it's most certain the console will reach 120M lifetime in the end. Software sales will be close to 1500M too, and profits coming from PSN section will put total software profits way ahead of what PS2 accomplished.
It's the best succesful/profitable console Sony has ever made, and there's really nothing more to say.