As the codecs where included in a previous version of an installed package (mesa) and no longer included in present version of said package, the codec support will go away when updating that package.
So yes, older systems will also loose the support, when the Mesa update reaches their branch.
The codecs are only for hardware accelerated decoding on AMD systems though (as far as I’ve read), meaning that video will still play, it will just use the CPU instead of the GPU to do it.