Of course, all extensions require developer support for them to be taken advantage of, and with this release AMD is announcing that the specification will be made available immediately. This will give developers a heads up for future processors that will take advantage of the spec. The processors that will feature this instruction set, however, aren't expected for release until two years from now:
The SSE5 specification, which is being made available to the developer community today at http://developer.amd.com/SSE5, will be implemented in products based on AMD’s next-generation “Bulldozer” core, available in 2009.
You can read the full press release at AMD's site.