The servers will come down for an update on June 10, at 13:00 GMT/ 9:00 AM EDT/ 6:00 AM PDT. (check this link to see when this is in your timezone). The downtime is estimated to take 2 hours.
This thread was added on June 09, 2020, with posts from AndyB.
The servers are online. Patch notes: Onslaught Update Patch notes