Booting off the network has been around for awhile. Old X workstations could boot using bootp and tftp.You can install Windows 2000 and above using RIS which uses PXE (basically DHCP and tftp). Sun sells / sold a workstation (SunRay) that booted from the
network as well. Even though network bandwidth is increasing, latency isn't decreasing so that will probably be the major factor in adoption of diskless workstations.