I don't see a chance for this to happen. Firstly because Parallels Desktop is virtualisation software and not emulation software. This means that within Parallels on an Intel Mac you can only install an OS that is written for the Intel platform. Secondly because the relatively small number of persons who would use Mac OS 9 with Parallels do not justify the effort it would take to implement PowerPC emulation in Parallels Desktop.
However, there is (free) software like Qemu or SheepShaver that does allow emulation of Mac OS 9 and earlier versions (look at emaculation.com). It does take a little more time to set up, though.
I would like to see Parallels Desktop to support macOS for Intel on Apple Silicon machines. Though this would really make sense for many customers, I don't think this is going to happen either, for part of the reason I already mentioned above: Parallels Desktop is not emulation software.