If you play Skyrim: Special Edition with mods, you've probably got Steam set to "only update this game when I launch it" in the properties menu, and you launch it from a separate exe via your mod manager of choice. If you don't, then every time the Bethesda Creation Club gets some new content, it breaks the Skyrim Script Extender (SKSE), a vital plug-in needed for several of the best Skyrim mods.
When Skyrim's 10th anniversary rolls around next month, you'll be able to buy the Anniversary Edition, which is basically the 64-bit Special Edition plus everything currently in the Creation Club and 26 more creations yet to be released. Even if you don't, the Special Edition will get some free creations (fishing, survival mode, and the Saints & Seducers quest). Rather than a separate entry in Steam, it'll be an update to the existing version. And it's apparently going to be even more of a problem for modders than the regular updates.
As one of SKSE's developers explains, "Bethesda has decided to update the compiler used to build the 64-bit version of Skyrim from Visual Studio 2015 to Visual Studio 2019. This changes the way that the code is generated in a way that forces mod developers to start from scratch finding functions and writing hooks."
While SKSE gets updated shortly after Skyrim does each time, other plugins aren't as well-supported. "I can probably sit there over a few nights and bang out an updated version of SKSE," the SKSE developer writes, "but my main concern is for the rest of the plugins out there. The plugin ecosystem has been around long enough that people have moved on, and code is left unmaintained. Effectively everyone who has written a native code plugin will need to do at least some amount of work to support AE. This realistically means that the native code mod scene is going to be broken for an unknown length of time after AE's release."
If the worst comes to the worst and mods you rely on end up busted after the Anniversary Edition update on November 11, Steam still lets you revert to older builds using DepotDownloader. One of the team working on mod auto-installer Wabbajack has also said they plan to come up with a downgrade modlist to achieve the same thing.
The recent surprise update to Fallout 3, which removed its dependency on Games For Windows Live at long last, was also compiled using Visual Studio 2019. That means the Fallout Script Extender (FOSE) isn't compatible with it any more, mods that relied on FOSE have stopped working, and one of its creators has updated the page to say, "I do not have a timeframe for when FOSE can be updated to this new version."