Wouldn't the logic to only hire Junior engineers if AI could do the work, what do you need the Senior salary for if they're both just asking AI to do things.
This is obviously assuming the ideology of an organization that would consider something like "We shouldn't be hiring engineers anymore" in the first place so they obviously have absolute trust in AI.
For now that won't work, based on my experience with LLMs, you still need a very senior engineer to prompt and review what was produced by the agent. A junior wouldn't have the experience to identify the flaws/issues.
In the future, yeah maybe, when LLMs are not as dumb as they are today.