I believe they said there would be another limited brewery only release in the fall and than at some point it will become a regular release seeing distribution.
I think it is safe to assume it is just not ready yet or they would have been talking about it across all of their platforms of social media. In the meantime, they did just fill some bourbon barrels with Impending Decent a few days ago....
I think Impending Descent is a very underrated beer. I don't hear much talk about it (maybe because it's seasonal). It is a fantastic RIS.
I do think it is a brewery only. I could be wrong, someone can correct me if so. They've done it two years in a row, so here's hoping to a third.