I would expect late this year if the production is enough.
We might get a repeat of the PS2 timeline (the first PlayStation with a Slim naming, but the PSOne model of the PS1 was technically a slimmer version)
PS2: 2000 PS2 Slim: 2004
PS5: 2020 P55 Slim: 2024
But if we get a repeat of the roughly 3 years for a Slim that we got with the PS3 and PS4, then your expectation will prove correct. But we have to look at context.
PS3 got a Slim in that time period because the PS3 was not working out and they needed a shift. PS4 got one in that timeline because the PS4 Pro came out around the same time (2 months later than the Slim) and Sony didn't feel like having 3 models.
Launching a Slim in 2023 makes some sense, but doesn't make as much sense as 2024.
Lifetime Sales Predictions
Switch: 144 million (was 73, then 96, then 113 million, then 125 million)
PS5: 105 million Xbox Series S/X: 60 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