It probably all depends on when PS5 lands, because launching a PS4 super slim after the PS5 launch is highly unlikely and possibly just a horrible idea.
If PS5 lands sometime in 2020, then it will be on 7nm, which would mean a 7nm PS4 super slim needs to launch by holiday 2019 at the latest. This is probably possible, since the fab yields should be high enough by then and since new console models tend to remain at the same price for a while before they drop, a $249 PS4 super slim shouldn't be all that out of the question late 2019, before dropping to $199 steady mid to late 2020.
If 7nm isn't quite ready yet and is too expensive, then 12nm/10nm could be used instead. This wouldn't allow for as small and efficient a console as 7nm would allow, but it would still be smaller than the 16nm slim console they have now. They could probably launch holiday 2018 if they wanted, since the fab yield shouldn't be a problem and should be cost efficient by now. A steady $249 PS4 super slim and $349 Pro slim going into 2019 would really help keep the momentum up. If the PS5 launched late 2019 or early 2020, with a steady $199 PS4 super slim announcement to go along with it, PS would be in PR heaven. If PS5 didn't launch until holiday 2020, then a $199 PS4 super slim for an entire year beforehand would sure tow the line until then.
PS1 - ! - We must build a console that can alert our enemies.
PS2 - @- We must build a console that offers online living room gaming.
PS3 - #- We must build a console that’s powerful, social, costs and does everything.
PS4 - $- We must build a console that’s affordable, charges for services, and pumps out exclusives.
PRO -%-We must build a console that's VR ready, checkerboard upscales, and sells but a fraction of the money printer.
PS5 - ^ -We must build a console that’s a generational cross product, with RT lighting, and price hiking.
PRO -&- We must build a console that Super Res upscales and continues the cost increases.
