The correct answer is: when they are ready.
I try not to swear, it sets a bad example 
Here’s the current plan as I know it…
Win v6 is in beta now and available to use if you have a Win Rhino v5 license. Next stop will be release candidates and then it’s very close to shipping. The Rhino for Mac v6 branch is only available internally now so we can begin work on matching the functionality with Win Rhino v6. There are lots of rendering bits and pieces to port so your question comes at a good time to make sure it’s on the list. Thanks for bringing it to my attention.
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