It appears that new patch versions of PostgreSQL RDS are being rolled out in AWS.. so we should expect an announcement soon:

REGION: us-east-2

  “DBEngineVersionDescription”: “PostgreSQL 10.11-R1”

  “DBEngineVersionDescription”: “PostgreSQL 10.12-R1”

  “DBEngineVersionDescription”: “PostgreSQL 10.13-R1”

  “DBEngineVersionDescription”: “PostgreSQL 11.6-R1”

  “DBEngineVersionDescription”: “PostgreSQL 11.7-R1”

  “DBEngineVersionDescription”: “PostgreSQL 11.8-R1”

  “DBEngineVersionDescription”: “PostgreSQL 12.2-R1”

  “DBEngineVersionDescription”: “PostgreSQL 12.3-R1”

REGION: us-west-1

  “DBEngineVersionDescription”: “PostgreSQL 10.14-R1”

  “DBEngineVersionDescription”: “PostgreSQL 11.9-R1”

  “DBEngineVersionDescription”: “PostgreSQL 12.4-R1”

… etc.