They must release it by this Christmas 2012 or earlier for Ubuntu 12.04 64 bit LTS. Valve knows that Canonical will release Ubuntu 12.10 on October 18th, 2012 so that will be the earliest release date for Steam for Ubuntu GNU/Linux. A lot of new computers will be sold and Ubuntu 12.10 32 and 64 bit will be installed on those new computers worldwide. I just hope that Valve knows what they are doing and they can guarantee compatibility for Ubuntu 12.10 regarding Steam.
This October 2012 will be an important one for me. I am probably going to upgrade to Ubuntu 12.10 64 bit, Microsoft Windows 8 Pro 64 bit, and Microsoft Office 2013 64 bit Professional Plus.
Then, we have the November presidential elections on November 6th, 2012.
Afterwards, Valve has one last shot to release Steam by Christmas 2012 at the very latest deadline to get Ubuntu users to buy games from them.
2012 will be a good year for me.