When is the Twenty Twelve theme coming out?

Hello,

I would be very grateful for any news on when the Twenty Twelve theme might be coming out. I have understood it will come with version 3.5 but is there any way of guessing when that might be?

I have been commissioned to write a book due out in Spring 2013, and of course I will need to write about the latest version of the default. If anyone can give me a clue as to the timing, then it would make my planning a lot easier.

Thank you!