Fmriprep HCP CIFTI output on existing data?

With the upcoming release of fmriprep version 1.6 which enables HCP style CIFTI output from fmriprep, will it be possible to run it on an existing freesurfer and fmriprep output directories to just generate the CIFTI outputs without re-running all the fmriprep processing?

Unfortunately not, as the CIFTI output will be in a different space from previous versions.