Following the release for developers last week, Apple has seeded the first public beta of MacOS Mojave 10.14.3. The beta build is available to those who have their Macs registered with the program. You can get more details here from Apple. If you have a device registered already, you can go to Settings>Software Update to check for the new release.
MacOS Mojave 10.14.3 is very much a maintenance update from Apple. No big changes to overall features are expected and, so far, none have been found. Instead, this update is focused on fixing bugs and performance issues that were in previous versions of the platform. That doesn’t mean Apple won’t sneak in a new feature or a tweak of an existing feature. It just won’t be the main thrust of the release.
You can expect to see 10.14.3 arrive for the general public sometime between mid-to-late January 2019. Apple generally goes through four to six beta cycles for MacOS updates like this one but that is subject to change if any big issues are found by testers. Usually Apple releases a new beta build every week or so while a new version is in this testing phase.
As a reminder, Average Apple Guy recommend that you not install beta OS builds on your production Macs. You could run into a bug that impacts productivity or worse, stability, on your Mac.