It seems that texlive contains an outdated package. I try to update the tex4ht package in TeX Live whenever CVR makes a release in tex4ht svn. Those TL updates can be retrieved with tlmgr, as well from TL svn. I cannot explain why you don't have it. It was updated in TL revision 27847.
The current version of biblatex.4ht in TL, and in the "upstream" tex4ht
afaik, is {version 2012-09-28-15:51}.
karl
