The servers will come down for a Hotfix on May 13, 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 May 12, 2020, with posts from AndyB.
Servers are back online. Here’s what’s been updated: Onslaught Update Patch notes