For version 1.2, we will not be publically documenting "Support for older version". However, we should still have a version 1.2 release note along with the new 1.2 mongosync binary. 

Let's keep the release note vague, like: "Version 1.2 - Support migrations for older versions of MongoDB. For more information about migrations, please contact your account team or at https://www.mongodb.com/contact."

The release notes are in the Google Doc at https://docs.google.com/document/d/1vDjeXw8x592d3NLKL5RHL6Nouw64heAL-yod_PyqKME/edit#

cc alex.komyagin@mongodb.com