If I had to guess, I personally wouldn't bet on a Day/Night cycle. I'm not too sure if we'll even get an anniversary updates because the last update was actually relatively recent.
Patch 6 was October 14, 2021
Patch 7 was February 15, 2022 (124 days later)
Patch 8 was July 7, 2022 (142 days later)
We are currently only 65 days since Patch 8. October 6 would be 91 days since Patch 8.
If we take the average of the last 2 gaps in patches, the next update would come Nov 17.
but patch 5 was July, 2021 that brings patch 6 just in 3 months plus unlock a new area.
patch 5 is a small though it's a meaningful update for dice system that cost 5 months. but the complete update is patch 6 for the anniversary huge update.
and I don't think patch 8 is a big project that needs to cost 5 months to be organized.
so patch 9 is possible coming October 2022, and might bring a new area unlock for 2nd anniversary.
