I was able to successfully upgrade the entire family (4 people) ATH-LHR on January 5th, 2024.

Upgrade cleared around 55 hours before the flight (7 hours before online check-in).

Business class was showing a 7 rows until around a week before the flight. Then it went to 5 rows, then 3 rows and finally, 4 rows at 3 days before the flight.

On the flight, business class was full. Not sure about Economy, but it also looked full.