From the original post:
After consideration, we have determined that there is enough interest to justify a fresh Kronos realm, and we are happy to announce that Kronos IV will be released in Fall 2021.
Kronos IV will be a progressive content server just as Kronos III (now known simply as “Kronos”) was, and will follow a similar content release schedule as the current Kronos server, with a server merge (Kronos and Kronos IV) to happen a few months after the release of Naxxramas on the Kronos IV server – so if you have characters that you are attached to on the current Kronos realm, do not worry. Both the Kronos and Kronos IV servers will remain online simultaneously, so you will be able to join in the fresh fun, as well as continue playing and raiding on Kronos if you so desire.