A note flagged “Important” atop the Xcode 27.2 release notes:
The iOS SDK and simulator support for iPhone Duo will be available later this month in an upcoming release of Xcode 27.1.
Adapting apps for the Duo is not just a simple “recompile with the new SDK”. It’s different. For just about all apps it’s going to be a significant amount of work, and for some apps it’s going to be a lot of work. But without Xcode 27.1, developers cannot get started. Developers wanted this SDK a week ago. And when day one preorder buyers start using their Duos on October 23, they’re going to wish Apple had shipped this SDK last week too.