I really do not think it is very probable at all. The PS4 definitely has the potential to sell as much or more than the PS1, but I do not think it is going to touch the PS2.
After all, the PS2 has a lot of conditions as to why it sold so much such as...
-Timed exclusive GTA games, as well as other third party exclusives
-Upon its release, it was the cheapest DVD player on the market
-Still plenty of incentive to buy it even after the PS3 was out (the PS3 had a rocky first couple of years)
-Backwards compatibility
Lifetime Sales Predictions
Switch: 161 million (was 73 million, then 96 million, then 113 million, then 125 million, then 144 million, then 151 million, then 156 million)
PS5: 122 million (was 105 million, then 115 million) Xbox Series X/S: 38 million (was 60 million, then 67 million, then 57 million. then 48 million. then 40 million)
Switch 2: 120 million (was 116 million)
PS4: 120 mil (was 100 then 130 million, then 122 million) Xbox One: 51 mil (was 50 then 55 mil)
3DS: 75.5 mil (was 73, then 77 million)
"Let go your earthly tether, enter the void, empty and become wind." - Guru Laghima
