Upgrading to macOS 27 no longer removes an existing Rosetta installation, according to Apple's enterprise release notes for macOS 27.2. Previously, upgrading to macOS 27 removed existing installations of Rosetta, the translation tool that lets Intel-based apps run on Apple silicon Macs. macOS 27 remains the final release with full Rosetta support. Apple plans to phase out general-purpose support starting with macOS 28.
Source: MacRumors · Summarized by HeadlinesBriefing