Its worth reading the recent post on Raspbmc, this is the relevant section.
First of all, as people keep asking about it. Netflix. This will indeed come to Raspbmc soon. As some of you have been curious as to how this is achieved I’ll briefly explain here. Another PC will unfortunately be needed to stream it. This PC will play the stream and capture the Netflix window, which will then be streamed over the network to the Pi. Although this sounds a little clumsy, it’s not that bad. You’re still able to browse all the Netflix content from your Pi, and when you select a video, your PCs browser will be opened, but playback will appear on your TV instead of your desktop. The issue that I am currently having is that I have no way of pausing, fast forwarding or rewinding the stream, so I need to think about how that can be made possible.
I wouldn't hold my breath, but it looks like something is in the works even if it does require a backend Windows/Mac computer.