It was a weekly thing, like 2-3 months ago. Look at when the original posts of these by Nachyo were made. They were weekly, but obviously, as it is the 12 weeks of lore, it only went for 12 weeks.

There will be one once the single player campaign mode is released (whenever that finally comes out).

I also thought that there was going to be some big lore related announcement at the end of the...

Sounds awesome. Hopefully though we won't have to wait for all 12 weeks before the expansion is released. That would mean another 3 months or so of waiting for DP to go live.