Of course when production of regular model ends also the production of performance model is ceased. Performance model (eg. RS4) can't be made without donor body, interior etc of regular model.
Being that RS / S, AMG, or M.
So, it's normal Audi will end RS4 production later this year!
RS6 has nothing to do with that ...
PS: avant and cabrio will continue to be produced for a further next months untill new A4 avant & A5 cabrio are introduced. So as an aftermath RS4 avant & cabrio will still be produced as well.