Or has it? So says Green Party Watch, anyway. Ballot Access News has a very short item, completely lacking in links.
For what it's worth, there's more detail on Wikipedia. The wiki also notes that this choice marks a return to Detroit after the Annual National Meeting there in 2010.
The decision was announced on the GPUS Facebook group page earlier this week. As of today, I can't find anything about it on gp.org, but the website crew may be waiting for more details to fall into place. There is also plenty of Election 2019 to discuss, and this year's ANM just ended a month ago.