Long time ago, when i did my ComSci degree, we were told that in the life cycle of software, on average, 33% of the programmer's time (ie the cost) was spent initially designing and writing it, the remainder was maintaining it, finding day zero bugs, adding end user requests, porting to new platforms etc.
I see AI being quite helpful in that initial stage, yes, perhaps it can do a good part of the initial writing, but not much of the initial designing. And almost none of the debugging / extending. Obviously that will change over time but some parts will always be harder for AI to help than others.
I can just imagine it, "hey AI, I want you to find this bug, here, I will fax you the source code....".
Davo