Valve's Hardware Survey for July 2013 shows an increase in usage for every recorded Linux distribution, with each distribution seeing increases between 7-22%. As every single distribution seems to be increasing in popularity, I interpret this to mean that as time goes on more people are trying gaming on Linux and they are staying with Linux.
|Distribution||Proportion of users||Increase as proportion of total users||Relative increase|
|Ubuntu 13.04 64 bit||0.43%||+0.03%||+7%|
|Ubuntu 12.04.2 LTS 64 bit||0.20%||+0.02%||+10%|
|Ubuntu 12.04.2 LTS||0.11%||+0.01%||+9%|
|Linux 64 bit||0.10%||+0.01%||+10%|
|Linux Mint 15 Olivia 64 bit||0.09%||+0.02%||+22%|
Note that due to the precision of data that is provided there are likely to be rounding issues, so the relative result in the right hand column could be +/- a few percent.