I have a feeling there will be a work around for Aperture in Catalina, like when they killed Final Cut Studio for FCX.
@GFS, I had not heard of RAW Power, the interface looks very similar to Aperture. If they included an Aperture like DAM it looks like it could be the first decent Aperture replacement.
Nope on the workaround from Apple. At least .. Nik Bhatt said it's highly unlikely, as Apple have said specifically that it won't run and as an ex-very senior Apple engineer, I guess he'd know. (I asked him specifically)
RAW Power as you probably guessed, was designed specifically to emulate Aperture going forward, following Aperture's demise. The crux is, that Apple have an excellent raw developer available in the OS, which they maintain for Photos and which apps can tap into. One of the cool things in RAW Power, is Nik actually explains really well, what the tools really do.