Now as we waiting for the soon to be released:
It becomes important to understand the differences between "clouds".
Public Cloud – Software is 100% controlled by SAP. You have very limited possibilities for making modifications while SAP implement carefully tested updates automatically according to a timeline determined by SAP. S/4HANA CE, SuccessFactors, Concur, FieldGlass, Cloud 4 Customer, Ariba and Hybris are public cloud systems. Cloud solutions can co-exist with on premise systems to create a “hybrid” system landscape. It is possible to make extensions to all systems in the hybrid landscape by using the SAP Cloud Platform.
I like this Public Cloud explanation which I found on the internet in a blog by Owen Pettiford: Public Cloud – This would be how my Mum consumes her SmartPhone, she comes to me and tells me what she wants, I set it up and she uses it. When she wants something difficult, I tell her that the phone can’t do that ?? S/4HANA Cloud Edition 1802 customised for Norway is delivered as a Public Cloud solution.This system can be set up quickly. It can be combined with your existing on premise systems to form a Hybrid landscape. The language and definitions are the same as in the on premise, with Company Codes and Plants as examples. It could be used to quickly set up a company which needs to be integrated into the existing landscape as an example.
Private Cloud is your own SAP system but 100% outsourced to SAP. This can be your Business Suite software (ECC) provided it is running on SAP HANA and can be made available through the Hana Enterprise Cloud. This is SAP ECC on a IT server which belongs to and is supported by SAP. ECC means SAP ERP Central Component (ECC) and is the SAP system that most SAP Customer companies still run. Updates are scheduled in advance and agreement with the customer.