OK, let us analyse here for a sec...
-Michael claims inside info;
-Michael claimed such a thing before with AMD so this is not new;
-Linux files have been found in public releases of the Steam CLIENT;
-Valve is on the porting tour with the Mac;
-Valve hasn't denied the client;
-Valve doesn't hate Linux as there have been Wine hacks inside of the Steam client before Wine was even runnable on the Mac;
-The Steam confirmation on their strictly monitored external intranet network has not been removed;
-The news has been everywhere and yet Valve did not pull the plug on the ever updated Linux binary on their public FTP server;
-There have been reports on closed beta Linux testing everywhere.
Are you guys stupid? It is being worked on in public... Valve doesn't plug it, so it's comming for 100% certainty. They have proved they can port to UNIX before so stop your doomsday theories...