For any component of Windchill, 'supported' isn't just from the perspective of PTC says 'it should work'. It also means the supplier of the component continues to update their product. ForWindchillDS, that includes support future Java versions (WindchillDS is limited to Java 1.8) and patching security holes as they are discovered.
Per CS337415, we can and must use WindchillDS during upgrade to 12.0.2. But once we pass 12.0.1, we should plan to move away from WindchillDS. PTC clearly states WindchillDS it is at end of life. From CS335696:
"The ownership and responsibility of maintaining the LDAP solution or migrating user data to any LDAP solution lies entirely with the customer."
and
"After the upgrade to Windchill 12.0.1, Customers should have a plan to migrate to an alternate Directory Server. Use of Windchill DS should only be considered as a temporary stop gap during the upgrade or in a non-production environment because PTC will not support any problems specific to Windchill DS."