True, Hashi can cask it just fine if they wanted to continue to distribute through homebrew. I doubt they would though, they have already been recommending direct binary installation from their servers for the past few years. That is how the installation documentation for Terraform has been for a while.

The bigger impact is on other tools that have terraform as a dependency, as seen here: https://github.com/Homebrew/homebrew-core/pull/139538#pullre...

Tools like atlantis and infracost are also getting removed since they depend on Terraform. So it is going to make distribution a little harder for those smaller tools. The good news is that the thread does say that they are holding off to allow those tools to update their dependencies to an alternative like OpenTofu when it becomes stable or to remove the dependency altogether. But the real impact imho is these other tools.