I found this an interesting read. Although holographic storage is years away and VERY expensive, it's worth reading.
http://www.cdrinfo.com/Sections/News...x?NewsId=21547
Of note is th following sentence:
"Call/Recall supports a patented 2-photon recorded 3D optical storage technology that can provide 40 times the capacity of Blu-ray. "
and
"HVD is backwards compatible with the Blu-Ray and DVD formats"
hd-dvd isn't even important enough to mention.