Some fantastic news to all who are waiting to get their Steam Decks, Valve posted a small update today mentioning that all Q3 orders have been fulfilled and Q4 is starting early! This means if you are in Q4, you should be starting to get your emails...TODAY:

Hello, just a quick note about shipping today.

As some folks on the internet have noticed (we see you Reddit!), we're speeding through reservations at an accelerated pace. This is due to increased production, and we've beaten our own estimates yet again. With today’s batch of emails we’ve now sent invitations for all reservations in the Q3 (July-September) bucket.

Now that Q3 is done early, we're going to get a head start on the next set of reservations, and are fulfilling reservations that were scheduled for the Q4 window. We've updated the store page to reflect this, with an updated bucket description: 

September-December.

That's it for today, more to come soon!

Quote from the Announcement posted to Steam.

You can view the above update and discussions over on Steam. Big HUGE congratulations to Valve on their increased production to get more Steam Decks in the hands of consumers. And to all new Deck owners, welcome to the family!