If you think about the capabilities/specs of Firewire, an Ethernet to Firewire adapter seems impossible.
With Firewire you can control your video camera, also a computer with Firewire has a dedicated Firewire controller so your CPU isn't doing the legwork during large transfers (as is with USB.) How any of this could be emulated over an ethernet port I have no idea.
All this seems to add up to a big FAIL with the new MacBook and video editing for many users. It's a real shame since the new GPU probably makes the MacBook suitable for even FCP.