I really hope they announce a special live stream event sometime in the coming week, kind of a beefed up version of the 8.3 reveal where they provide us with a massive update of progress since BlizzCon and announce the launch of Beta.
Update on Covenants, Soulbinds, etc. along with art of transmog items, mounts, etc.
The Soulbind system is developed to be more or less this expansion's version of Artifacts, with lots of added abilities for your class, inspired by heroes of old so they don't feel generic but rather class-specific. If a Paladin soulbinds with Uther, for example, it'll unlock a few abilities one would expect Uther to use. As you play the expansion, your connections to your Soulbound characters deepen as you do quests for them all over Azeroth, letting you explore those characters' past. This unlocks more powerful abilities.
Covenant abilities are no longer proper abilities, just cosmetic enhancements of other abilities for your class. For example if you want your Hunter to look and feel more like a Dark Ranger then it's fitting to roll Venthyr as you'll make your spells and abilities look a bit more dark and sinister. If you want your Druid to feel even more druid-y, then going with Night Fae might let you sprout antlers in Restoration spec, etc. A troll Shaman might want to feel more Voodoo, so Necrolords could be a good fit to get more bony and dark, swirling spells.
Showcase of new customization options for several races, including San'layn for Blood Elves and High Elf options for Void Elves.
These richer options are unlocked through quests much like the Night Warrior appearance for Night Elves. As a Void Elf you need to undergo a secret ritual with Vereesa Windrunner to restore your natural appearance before turning into a Void Elf, and as a Blood Elf you aid a few renegade San'layn to defeat a cult of vampires in Revendreth that are plotting to overtake the entire Blood Elf race. In the process the evil ones turn you into a San'layn, but you defeat them and are accepted back into Blood Elven society along with the other leaderless San'layn seeking a home.
Announcement of two new Allied Races.
Lightbound Undead for Alliance and Saberon for Horde. Clarification that Undead on Horde at the ones who grew attached to the Horde and feel like their ties to the Alliance have been fully cut, whereas the Lightbound Undead feel like the return of Calia Menethil is reason to reunite with their living family members on the Alliance. They are intrigued by heir vision of a redemption. The Saberon are the ones who arrived through the Dark Portal with the Mag'har Orcs. As for the Botani who arrived at the same time, we're given a tease that they've a newfound interest in the potential of restoring parts of Azeroth. A sort of tease for the future.
Announcement of a fully revamped Professions system.
You are able to craft unique items and treat it as a proper endgame system. Legendary crafting and so on. If you are prepared to grind and gather tons of materials or farm unique recipes, then you may also unlock really rare transmog appearances which could net you a good sum on the AH perhaps. This could follow the same theme as the rest of the expansion, of heroes from the past and so on. Perhaps one unique set to unlock could be Kael'thas armour.
New heritage armours.
Reveal of two new Heritage armour sets coming with the launch of Shadowlands: Night Elves and Undead. More to follow in patches.
I could go on but... damn, suddenly this thing is beginning to look like a proper expansion in my eyes.