I think there are some people who won't pay for software regardless of the platform. These people might be tempted towards Linux because of its free nature. But as Linux becomes more mainstream and fair paying users start to use it then the games market will really take off and Linux will become the killer platform for the next few years.
But in order for the users to move, there have to be games. This situation is improving all the time as more and more games are ported and released.

Not all Linux users are in it soley for the freebies. The last game I purchased was Unreal Tournament 2003 soley because it shipped with a Linux client. I'm considering buying Neverwinter Nights too. Also, I'm a WineX subscriber. The subscription fee is a small price to pay to enable me to play my old Windows games on my PC and if the money allows more games to be played on Linux, more people will consider switching.

Just my opinion.