As of release 3.,8.14, there are a couple of places in the class methods where special code is in place to gracefully handle backwards compatibility.
Because of where the changes are in the class construction it is not practical to use the wpsc-deprecated file. The code does give a deprecated warning, and will eit in a manner similar to an undefined function if deprecated processing is not enabled. That should make it easy enough for third-party developers to find.
The special code has been conspicuously commented and refers back to this specific issue so that some reasonable amount of time/releases into the future we can remove the special purpose backwards compatibility code.