I am sorry but we can not post more detailed road maps here because some of this information is confidential. You would have to contact your local B&R representitive for that information.
Overloading is not part of the standard, so that would probably require a feature request.
The only thing that supports overloading are the standard ANY ST functions afaik.
Interfaces will be implemented. Don’t know where we are at there at the moment.
We will implement ST-OOP as per the IEC 61131-3 standard.
Anything extra is either coincidence, historic differences of B&R ST syntax or easy to implement due to cross compilation to C++ upon compiling the ST-OOP code.
Or explicitly requested by someone and approved by the product management.