The build number of today's update is 16C32f, while the original 10.12.2 beta build number was 16C32e, indicating a small incremental update that does not count as a full second beta release.
Because the new beta is not showing up as an over-the-air download in the Mac App Store for developers who have already installed macOS Sierra 10.12.2, it likely only includes minor tweaks and will be provided only to developers who are downloading the beta for the first time.
macOS Sierra 10.12.2 includes the same new emoji and emoji updates that are present in the iOS 10.2 beta, introducing support for Unicode 9 emoji and new profession emoji. Some of the new emoji characters include selfie, face palm, crossed fingers, shark, owl, butterfly, bacon, avocado, and croissant.
Apple has also updated many existing emoji with new artwork, adding detail and making them look brighter and more realistic.
The 10.12.2 update also includes under-the-hood bug fixes and performance improvements to address issues discovered since the release of macOS Sierra 10.12.1.
Update: The macOS Sierra 10.12.2 update is now available as an over-the-air download for developers, but it is still labeled as "Beta 1."