Information about usage of XProc 1?

Hi, XProc users.

The XSpec repository contains XProc pipelines for running XSpec test suites. I'm wondering whether future versions of XSpec should continue supporting its XProc v1 pipelines, now that it has XProc v3 pipelines. Does anyone have data, anecdotal evidence, or opinions regarding the community's reliance on XProc 1?

Thanks,
Amanda