SoM Transfers

You read this right?

When Season of Mastery concludes, you’ll have the option to permanently transfer your character to an existing Classic Era realm in your region. This free service will become available for a limited time at the conclusion of the season.
While we don’t yet know the exact destination realm and specific dates, you’ll have plenty of time to move your character to a safe home before all Season of Mastery realms are permanently closed.

Notice the words “concludes” “Conclusion” as in at the end. That’s 3 months away. A quarter of the life of the realms. They later added Wrath to that.

Since the very beginning of Season of Mastery the topic of where seasonal characters would end up when the season ends has been a hot topic of discussion for not only the community

As for timing, this is still quite a ways off and will happen sometime well after the release of Naxxramas in SoM.