Microsoft has released the 64-bit version of the Directory Synchronization tool for Office 365.  The community post is here, so please do go and take the time to review the information presented there.  However, I'd just like to call out from the community post the following statement : "...the functionality of the 64-bit version of the directory synchronization tool is identical to the 32-bit version...".  This obviously means that the 64-bit version does not contain any new features over the 32-bit version, which in turn means that if you are currently running the 32-bit version, there is no real need for you to go and download the 64-bit version as a replacement; the 32-bit version will continue to function.