I think plagiarism’s going to help raise the bar in songwriting and musicianship. It’s not enough to write your own songs but also avoid plagiarism. Either you come up with your own ideas or peruse the public domain and credit the original writer, if it does exist at all. This has been done before, just not en masse. However a lot could change following what would be deemed the biggest plagiarism scandal.
It could even affect other industries like clothing where they have to turn to other sources of inspiration outside of fashion more often. Public domain becomes more popular than ever, it’s legally and artistically free. Two musicians can base different versions after the same poem by Edgar Allan Poe and not sue each other for as long as the melodies differ.
It’s weird to have a Top 40 pop album containing nursery rhymes but in this environment it’s possible to do it and still be successful. People would take time to adjust to it but that’s because it’s the new reality.