So those of you on the Handelabra mailing list should have gotten a mail yesterday with a Sky-Scraper video, and the "announcement?" that Wrath of the Cosmos is coming "soon".
So, the real question is.......when is soon?!
When it's ready is the best answer you'll get.
Sometime after the Twitch Livestream previews are done.
Not that this means correlation, but Shattered Timelines released about 10 days after the Listening Party.
The Listening Party for Wrath of the Cosmos is next Tuesday, April 5.
So possibly in the next 3 weeks?
Or possibly not.
They've demoed all the new decks except Enclave of the Endlings and Kaargra Warfang (EDIT: and Progeny). I have hope it'll be before the end of April.
Wait, they have? When did they preview Progeny or Deadline?
Deadline was in the second preview - the week after Dok’Thorath.
They have not previewed Enclave, Kaargra or Progeny.
Enclave will be previewed in next week’s livestream.
The fact that they previewed both Cap Cosmic and Infinitor together in this week’s livestream suggests to me that they are getting closer to release 
Oh, I see. It appears to be missing from YouTube, which is why I missed it.
Deadline was hosted through another channel on twitch and thus didn't make it to their YouTube channel.
You can find it linked in our #SentinelsLive Season 7 playlist here:
https://www.youtube.com/playlist?list=PLGPBmjNUB43jrBuz_XUN1n4aWqyL-4v3t
Whoops, I forgot Progeny, sorry. D:
Some fun numbers:
The first preview of Mini-Pack 1 was 90 days after Sentinels Digital was first released.
Mini-Pack 1 was released 23 days after the first preview.
The first preview of Rook City was 19 days after Mini-Pack 1 was released.
Rook City was released 49 days after the first preview.
The first preview of Infernal Relics was 21 days after Rook City was released.
Infernal Relilcs was released 62 days after the first preview.
The first preview of Mini-Pack 2 was 102 days after Infernal Relics was released.
Mini-Pack 2 was released 35 days after the first preview.
The first preview of Shattered Timelines was 25 days after Mini-Pack 2 was released.
Shattered Timelines was released 43 days after the first preview (8 days after the Listening Party).
The first preview of Wrath of the Cosmos was 41 days after Shattered Timelines was released.
The listening party for Wrath of the Cosmos is 28 days after the first preview.
One item of note in your list is that the gap between Infernal Relics and mini pack 2 was because they started working on and released multiplayer.