Hopefully this will finally put an end to the belief that PS consoles are incredibly long-lasting
There's no reason to end that belief, data clearly shows Playstation consoles are long-lasting, it's an indisputable fact. Xbox 360 being the console with the best legs.
|First 5 Years||Lifetime||% of sales after first 5 years|
|PS1||72.97m (March 2000)||102.54m||28.80%|
|PS4||86.465m||113.9m||24% (still increasing)|
|Xbox One||39.39m||48.55m||18.8% (still increasing)|
As for the actual post-successor focus of your thread, this boils down to PS4 vs 3DS which you could have put the data for in your OP.
3DS post successor sales were 11.3m, meaning the ps4 needs to get to 125.1m lifetime sales to beat it's post successor sales. It certainly won't be that easy but with PS4 support going into 2021 (Horizon 2), it's certainly not impossible either.
PS3 managed 8.19m post successor, 11.3m for PS4 post successor is easily feasible.
60/40 in favour of 3DS.