Although 64 bit DT plugins are built, exist in the windows 64 bit java bundles, and can be used by 64 bit versions of IE and FF browsers, there is one remaining sever limitation.
When Installing Java, the plugins download the single file, dtoolkit.xml, from java.com/inc/dtoolkit.xml.
This file has pointers to bundles for various versions of 32 bit java.
The result is the attempt in 64 bit browser to install additional java versions will always result in installing 32 bit versions of java, unusable in that browser.
This should be addressed in 7-pool.