The key event of IDF Spring 2004 was the offcially announced support of 64-bit extensions in the future Intel's IA32 desktop, server, and mobile processors. Before the official announcement this technology was codenamed Yamhill, but after that obtained the more sonorous name, Clackamas Technology. Specialists however prefer calling it IA32E...Full article at Digit-Life
On the future of x86 64-bit extensions

Digit-Life wrote a big article about the future of 64-bit extensions..