Elasticsearch 6.1.2 is the minimum version planned for PeopleTools with release 8.57 (more information on that coming soon). In addition, 6.1.2 is also planned for availability on PeopleTools 8.55 and 8.56. Upgrade to Elasticsearch 6.1.2 will require full indexing of all search definitions. Customers will be able to use the Live Cutover feature in the PeopleSoft Search Framework to migrate to Elasticsearch 6.1.2 with no downtime.
If you are using Elasticsearch 2.3.2, and want to continue on it, that version will be supported for one year following our support of version 6.1.2. At that point, Oracle will only support version 6.1.2. Note that support for PeopleTools 8.55 ends before October 2019, so Elasticsearch 2.3.2 and 6.1.2 support for 8.55 ends with the last CPU for 8.55. At that point no fixes to the PeopleSoft Search Framework or Elasticsearch will be available for 8.55.
Look for more announcements on this important transition including new features for Search that will be available with PeopleTools 8.57. These will be posted on the Search concepts page on peoplesoftinfo.com.