It’s not about replacing all programmers. If one programmer with AI assistant can do work the same as 2 programmers then one position is redundant.
Even with self driving truck if one truck driver is leading another truck behind controlled by AI, and just for safety you have somewhere C&C center with one person monitoring 4 such ai trucks and in case unexpected event remotely take over control then one truck driver position is redundant.
While I do think there is some threshold where increased productivity makes positions redundant, I don't think 2x would do it in most orgs. My current team easily has enough work for us all to be 2x more productive.
Even with self driving truck if one truck driver is leading another truck behind controlled by AI, and just for safety you have somewhere C&C center with one person monitoring 4 such ai trucks and in case unexpected event remotely take over control then one truck driver position is redundant.