A new (and hopefully improved) version of Sigma PhotoPro for the Merrill version of Sigma dp1-2-3 cameras and the new quattro cameras is available at the Sigma global website:
http://www.sigma-global.com/en/download/cameras/sigma-photo-pro/though not yet on the Sigma USA site. It functioned OK in a quick check of converting a few dp2m files, but I haven't yet explored it further.
Regards, Rick