It looks like a major update to {ggplot2} is coming (version 4.0.0), where Posit is switching the internals from S3 to S7. This will break many reverse dependencies of {ggplot2} (a reverse dependency is a package that depends on {ggplot2}), and so Posit is following the recommendation of the CRAN policies, which state that they should give a heads-up to devs of reverse dependencies and give them …