Tax Update 18-A has posted for all releases (the update for 9.2 is included in HCM Image #25). For posting information and links, see Document 2347522.1 on My Oracle Support.
Subsequently, the 2018 Tax Rate changes have been posted for all releases. You can find links to these postings on Hot Topics, Document 1348833.1 on MOS. Tax Update 18-A is a prerequisite for Releases 8.81 - 9.1. If you downloaded 9.2 Patch 27377851 prior to the posting of HCM Image #25, you can apply to Image 24. Once the new image is posted though, you need to apply to the current (25) image.
Finally, we'll have our Tax Update Advisor webcast on Tuesday, January 23. You can see schedule and register here: https://community.oracle.com/thread/4105309