If they choose to discontinue it, it would be nice to have them opensource it so that the community could have a go at maintaining it tbh. Surely that's better than letting it rot (both rosetta and the old software that it runs).

That would be ideal, but given Apple's general hostility towards Open Source, it sounds extremely unlikely. I wonder what it would take to re-implement it. If it's "just software," I suppose there is a chance, not that I'm volunteering :)