"Or are companies doing this on the expectation that AI is advanced enough to pick up the slack?"

I think it's the expectation. We have some publicized examples of needing to hire people back. My company isn't laying off, but they also aren't hiring much, especially at the entry level. They're also trying to force attrition with PIPs and stuff. If it was a right now thing, they'd just layoff.

Also, just because coding gets 30% faster (say some studies), doesn't mean that's a 30% reduction in headcount since many tasks are about design and stuff. This seems to further point to a lack of hiring being anticipatory in my estimation.