Okay, so we didn’t get any new information in XO19…
But all is not lost, because there are so many secrets left to discover in the Halo Infinite Game Engine Demo and Trailer - not least, many “Memories of Reach” as well as of Halo 1 to 5 used to create the Engine Demo’s Storyboard…
The article below reveals some of tricks needed to unlock those hidden meanings and see something of Dan Choshek’s and the 343i Team’s Game Engine Demo Mini-Story as well as understand more about how 343i tell stories in their games like Halo 5. It also hints how Halo 4, 5 and Infinite might join together in the larger “Reclaimer Saga”. I hope you enjoy it and learn a few tricks about how to get more out of 343i’s games, as well as other games and movies (not least the new Star Wars movies)! 
https://sway.office.com/cAjX6e5YqdbDdxyd?ref=Link .
Note to Monitors: please don’t move this to “Community Creations”, as it is simply an analysis of hidden clues and meanings of the Infinite Trailers meant directly for the Infinite Forum, and which wouldn’t be easy to create as a regular post…