We found out when patch 11.0.7 arrives today, with a December 17th launch date. And now we also know how long it will take us to unlock flying in the new zone as well!
In a small update to the PTR development notes, Blizzard clarified that it will take us 6 weeks to fully update the 
Cyrce’s Circlet. The final upgrade will then unlock flying on Siren Isle as well, as we’ve already covered.
The 11.0.7 PTR has been updated.
ANSWER THE CALL OF SIREN ISLE
- For quicker PTR testing, we progress through the content faster on the PTR. Please note: When this content goes live, players will unlock different ring powers weekly over six weeks, leading to the ability to fly once all is completed.
IF you’re wondering how we’ll get to the isle, head on over here and find out!
