Similar discussion is also going on here.
See FAQ here.
Q: When do I get the Update?
A: We are providing the Android 9 in batches - each with a limited amount of users, starting on March 25th, 2021. We expect that all devices still in use shall have received the notification for the update in May, 2021. This controlled roll-out enables us to quickly react to possible bugs and issues that arise in the field.