same applies for seniors as well. ther isn't much distinction of senior vs junior human dev (as in cost and efficiency) compared to AI-dev (cost and efficiency). more so, at current imrpovement rate. in couple more years you would not need seniors anymore either.
As long as architectural decisions have long-term costs and you need human taste and judgement to speculate on what business needs will come about in the next few years you'll still need human engineers.
This seems pretty unlikely. If it turns out to be true then you don't need a junior or senior dev you can just get a random person from the street and they could do the job.