It is a shame that it is just a rumor but really that's all it's been for the last half decade. Plus, Phoronix refuses to release this binary their meant to have found which I tend to think means they don't have it. Steam for Linux would really be a huge win for native gaming but from Valves point of view it might be too risky?
A better solution which you'd hope they'd approach Codeweavers or the likes of Ubuntu about would be integrating Wine into a native Steam to run Win32 binaries of non-native games. On top of native Source games that is. This would be pretty easy, and using the Steam first-time-run script system we could actually make a native version support Win32 binaries via Wine ourselves (if it agreed to download and install them!).
On the Steam topic I should note that Steam is now at the point where you can run it in the background 24/7. There is a patch that allows you to buy things via the Steam store and using the latest Beta Client update from the opt-in menu removes the last couple of CPU intensive problems with running it (this is distinct from the new UI update).
I've had it open for the last week just like a native program and it's great to catch up with friends playing various games instead of them having to tell you to login and join!