Maybe they would need to tweak their policies a little bit to cut costs in order to make it happen sooner?
Basically GOG has to decide whether they want to put emphasis on growth in the future or profitability now and whether support of Linux makes sense or more games for the Windows plattform. After all their internal resources are limited.
What I don't understand is why they aren't offering the native Linux versions existing for many newer games they are selling. Just introduce Linux support on a piecewise basis. For me it seems like a waste of potential sales at almost no costs. I don't see the economic advantage of not doing it.
Well, with a competitor that offers Linux games the issue for the customers is less severe now. Everybody just go to Humble Store and buy DRM free Linux games there. No real need to complain anymore, except for those games which aren't there.