what's going on?
WeakAuras will not be updated to support the Midnight expansion. We will continue support for The War Within until the 12.0 patch.
wait, really? you can't be serious

Yep, sorry.
but ion said they weren't killing WA, so why are you doing it yourselves?
In short, it's because it seems the core value proposition of WeakAuras isn't compatible with the direction Blizzard is taking the game.
what exactly is blizz changing?
Broadly, all of what you might call "combat state" is now inaccessible. An addon can instruct the game to display this information, but is not free to compute any kind of fancy logic. Unfortunately, "empower laypeople to compute fancy logic about the combat state" is exactly what WeakAuras offers above all else. In Midnight, it seems that addons are reduced to being mere painter's kits.
We can change the color of a health bar, but we can't change the color based on if you're low health or not. We can display an icon with a spiral to show the remaining cooldown of an ability, but we can't apply a glow when the cooldown becomes ready to use. We can show the cast of your target, but we can't highlight important casts which need to be kicked. And the list goes on.
why don't you just limit WA to that "painter's kit"?
Honestly? It makes us sad. We're looking at stripping out essentially every feature added in the last 10 years, and more besides.
We've prodded & poked & tinkered & toyed with this big messy thing called WeakAuras for much of our adult lives. The idea of destroying all that for the sake of keeping WA alive just feels wrong. Instead, we would prefer that WeakAuras dies in the best form we could make it.
what would make you reconsider?
There are a few things we can think of:
the ability to compute new secrets
To go into the technical details a bit, combat state APIs no longer directly return information addons can use, but rather return "secret" values which can be piped into other api which interpret those secrets to display combat state to the user without exposing it to the addon itself. You might have heard of private auras before, and secret values can be considered as an extension of that to the entire combat state.
Blizzard maintains that addons don't necessarily need to see all that information, and for WeakAuras I'd agree, if addons could compute new secret values. As an example, if it was possible to do things like combine "is the ability Icy Veins on cooldown" and secret "is the buff Icy Veins not active on the player" into the secret "is the buff Icy Veins not active on the player AND is the ability Icy Veins on cooldown", then we could retain much of the utility of WeakAuras.
Unfortunately, we did already ask about that, and it was indicated to us that it's very likely policy that Blizzard doesn't want exactly this kind of power in addon's hands. Best as we can tell, this is a philosophical stance along the lines of players shouldn't need addons to fill gaps in the information the game gives them, and Blizzard seems like they want to ensure that is the case by making it impossible for addons to fix those kinds of mistakes. Put that way, the changes are almost admirable, but it does put WeakAuras in a weird spot, since "fixing gaps in information" was our bread & butter.
revert this change for personal combat state only
Before this week, we'd assumed that personal combat state (so, your own buffs, cooldowns, resources etc) would still be available, and that WeakAuras would converge into something like a hyper-customizable Cooldown Manager. We think this is still just about plausible, and while it would be a severe reduction in our capacity compared to before Midnight, we would still be willing to maintain the addon in this scenario.
revert this change entirely
Sadly, this possibility is extremely remote at this point. "Addons gone" is all but a flagship feature of Midnight at the point, them's the breaks.