"a debilitating limitation of Sony's SonicStage based Hi-MD upload function:
audio upload is only possible into DRM-locked files or ATRAC3 CDs!.
Fortunately Sony has stated that a standalone Wave Converter application
will be available in autumn that will allow Hi-MD mic and line input
recordings to be uploaded and exported to open .wav files, as they promised."
See http://forums.minidisc.org/viewtopic.php?t=5417 for more information.
My two cents: Don't hold your breath.