Hey there
Please see Foundry VTT version selection for an explanation of the release channels on Forge.
There’s no specific timeline until Forge recommends v12, and it depends on several factors, one of which is the rate at which module developers release updates to add v12 support. Once v12 has had a bit more time in the wild, we expect the the v12 module ecosystem and the supporting modules around the majority of game systems to stabilize. We are also resolving certain internal integrations like changing our Foundry log viewer to work with v12’s new log format.
Once more time has passed, and we anticipate a smooth transition for users running their games on Forge, we’ll re-assess and may move v12 to recommended. I personally don’t expect this process to take more than a few weeks, but of course I can’t give a hard timeline on that.
It’s important to note that you are not prevented from using v12, even if it is not yet recommended, and that some systems and their supporting modules may move to support v12 faster than others.
Hope that helps!