I'm not sure what happens in the short term, but WOW margins are still at world record highs for supermarkets.
There would have to be a permanent unique reason for this, otherwise you'd expect them to be challenged, as is happening and mean revert.
Woolworths won't maintain the margins unless management start making good decisions. Changing supermarket upper level management was a good start. They have been doing well but the problem for Woolworths is that, at least for the last few years, they have tried to keep growth up by cutting the amount of staff on the floor in their stores. You get to the point where you can't cut anymore. The issue is cuts take a toll on customer service as well. They weren't willing to reduce dividends and see the stock price fall and focus on increasing staff productivity and then cut when there are genuine redundancies. Most people go away feeling they are now doing the job of two people and end up quitting, especially if they are doing 80 hours a week on a salary. It may be true that they could do more work but Woolworths continually throw staff in the deep end instead of training them how to do their jobs better so that they can get rid of staff. At this point a lot of work gets put on salaried managers. Since they get in trouble if they don't perform the required work within the legal limit they are allowed to work, they have to clock off and continue working. I have heard of a manager (who would have only been on 50 - 60k) once working 18 hours straight.
The discontent at the bottom will end up coming back to bite Woolworths if they don't change their ways. They did recognise a morale issue but their solutions to it have been questionable - painting lunch rooms and forcing staff to do surveys which just told them people weren't too happy (painting lunch rooms is an odd choice when some management don't even get lunch).
Fortunately for many wow employees, at least the ones I know sold out their shares when they were above $33. One manager said he didn't since he is adopting a buy and hold forever approach but he was relatively young with a young family. Others were out of there since they could see the writing on the wall from the store operations level. Maybe they were wrong though and maybe the new upper level management can guide the company to actual growth rather than just cost cutting.