Exchange 2013 CU 21 was released on June 18th 2018 and is the latest release of Exchange available here.
.NET framework 4.7.1 is now a pre-requisite.
Exchange 2013 CU21 and onwards also requires VC++ 2013 runtime library.
Ne wExchange Management Shell commandlets are available to create and manage shared Office 365 shared mailboxes in Office 365 Hybrid Environments.
While CU21 does not add any new AD Schema changes. That said, if you are on an older version of Exchange 2013 schema updates may be required to get to the level that CU21 requires. It appears if you were on CU10 or newer you will not be required to update the schema.
Resources:
Schema revisions list: https://blogs.technet.microsoft.com/rmilne/2015/03/17/how-to-check-exchange-schema-and-object-values-in-ad/