"Hey Siri" support and possibly wireless charging case alongside AirPower charging mat.
Apple Seeds First Beta of iOS 12.1.2 to Developers With 'Bug Fixes and Improvements'
Apple's release notes state that iOS 12.1.2 "contains bug fixes and improvements," so this appears to be a minor update.
Registered developers can download the new iOS 12.1.2 beta from Apple's Developer Center or over-the-air once the proper configuration profile has been installed from the Developer Center.
We'll update this post if we discover any notable changes.