AMD hasn't officially confirmed this but people at the XtremeSystems Forums found out Intel has a very similar technology called "Core Multiplexing Technology" (CMT).
AMD has yet to confirm anything of the sort, but the folks over at the XtremeSystems Forums have made an interesting discovery pertaining to the Intel side of things. A new BIOS for Intel 975X motherboards seems to add a "Core Multiplexing Technology" (CMT) option, which some user-created diagrams suggest is a sort of reverse Hyper-Threading feature:More info over here.
If Intel manages to kick off Core Mulitplexing in time for the Core 2 Duo launch and AMD follows along as rumored, July could be an interesting month indeed.