My current thinking is they might throw out a verbal teaser that maybe teases at the general theme of the pack and when we might expect a formal announcement. This would prime the pump for their socials, keep people chatting, etc. And, especially given that they've already posted that console trailer twice I just don't see a PC DLC reveal today, sadly.
I'm also just not thinking they do any sort of major reveal on the stream. That's big enough that they would be a bit more direct in the announcement to get people watching. But they don't get much benefit from a split-platform livestream compared to, say, dropping the trailer on YouTube and their socials.
So my guess now is a tease today with a reveal on a later date.
But file this one under: "I want to be wrong."