SAP ECC(ERP Central component) is the core of existing SAP Business suite. SAP Business suite has SAP ECC+SAP CRM + SAP SRM + SAP SCM + SAP PLM . SAP ECC to not be confused with SAP Business Suite . SAP ECC is part of SAP Business suite. SAP business suite will run on any db ( Oracle, MSSQL, IBM DB2 ) including HANA.
SAP HANA is an RDBMS like Oracle, MSSQL, DB2 etc. Speciality is, it's an in-memory, column oriented database.
S/4 HANA stands for SAP Business Suite four SAP HANA - The backend application layer runs on solely HANA db and front end will be developed with SAPUI5( Fiori). In the 3 Tier architecture of SAP system, HANA is the database layer, S/4 HANA is the application layer, Fiori is the presentation layer.S/4 HANA is called the SAP Next gen Business Suite.
Concept of SAP ecc isn't here. Instead modules like Simple Finance, simple logistics etc +SAP CRM + SAP SRM + SAP SCM + SAP PLM . It is an on going project and different modules will be optimised to run exclusively on HANA.