I think it’s a “when it’s ready” type of a schedule. I imagine it will be part of a 24.x release. You can try it out if you want to see the sausage making: https://github.com/pop-os/cosmic-epoch

One of the devs posted a response to this question in this thread, since I asked the same question: https://sh.itjust.works/post/69204
If you are technical, you can start playing with it now but no estimate when they’ll have an ISO ready.

I’d guess it’ll be ready to try for most users by early next year… there will likely be an alpha before then though.

Hopefully on the same moment as the Virgo laptop.