Any customers currently using SOAP calls should start planning to replace them with REST calls. This needs to be done prior to upgrading to the MFT 8.4.0 release.
Soap calls are used in the following ways:
1. BW5 or BW6 admin SOAP calls
2. Customer applications that use Admin or FileTransfer SOAP calls
3. Command Line Utility. Note that the MFT 8.3.0 Command Line utility will be REST based, not SOAP based.