The Enterprise Cloud Suite will automagically change into Secure Productive Enterprise on 1st October 2016.
SPE will be available in two flavours – E3 and E5 – and ECS becomes SPE E3. However, it also gets some new rights including the ability to install the server software for Exchange, Skype for Business and SharePoint on on-premises servers for SPE users (useful if you need to deploy further servers on your way to the cloud) and the From SA USLs also include the rights to install Office Professional Plus on one device.
The official Microsoft page is here: http://bit.ly/2cIWgkh.