While gigabit networks are still relatively new in both the workplace and home, with 100M being the defacto standard, the IEEE is already looking to the future. The IEEE's “High Speed Study Group” has being toying with several potential standards and has settled on 100G as the next step. Of course, that's just the direction they want to move – it says nothing about the practicality of such a feat. That's why the next step will be to find out exactly how to make that standard possible:

With the approval to move to 100G Ethernet, the next step is to form a 100G Ethernet Task Force to study how to achieve a standard that is technically feasible and economically viable, says John D'Ambrosia, chair of the IEEE HSSG, and scientist of components technology at Force10 Networks.
A standard will take years to be created and ratified, so the earliest we'll probably see developments of this nature will be in 2009 or 2010. A need for faster Ethernet is recognizable, especially with the increased focus on web-delivered live content. The interesting part is that no existing technology is capable of delivering these speeds. The article speculates on what could deliver it, such as multiple 10Gbps lines bonded together. Interesting stuff. When technologies like this are available, most likely it'll be focused exclusively on transport, for large backbones.