Holy mother Spiderman sold really well, it is clearly going to become the best selling playstation exclusives, 14 million is nothing when it did 9 millions in 3 months with still christmas to go and several sales.
The numbers for the holiday are a bit disappointing tho, but it was expected since they didn't have like any great deal this year. Vgchartz is overtracking it at the moment but i think we all knew that from the predictions from benji.
For the upcoming year, i don't see it perform quite as well as 2018 but not dropping too hard either. I think if it manage to sell 16 millions it would be amazing. We don't know about the big titles coming this year and Sony not showing at E3 doesn't seem like they will have much to release either. 2018 had several huge system sellers like Monster Hunter for japan and GoW and Spiderman for the rest of the world. Freaking spiderman that is going to become the best selling PS exclusive couldn't save the holiday numbers with it's bundle and made it the worst holiday for the console after 2014 and 2013. I think that it might be an indicator that if they don't drop the price, the console will not pick up like past years and there isn't as big system sellers in 2019 (as of now) compare to 2018. KH3 is really bigger than y'all make it seem and with all the re-releases and the announcement 4 years ago i'm sure people already have a ps4.
So for short my prediction is :
2019 : 14,5 to 16. (14,5 if they don't drop the price and 16 if it drops)
2020 : 8 millions (next gen will be announce and released so honestly it's expected to have less exclusives and focus on the PS4 to prepare for launch and not outshine the PS5 with great PS4 deals during the holidays etc. )
So it will, imo, make it between 110-120 lifetime, just enough to beat the Wii and the PS1 which is incredible.