While I can't comment on how companies take online petitions, I do think that many of the big players have been keeping an eye on Linux as a platform to develop for. As others have said - wider audience = more chance for sales.
I think that there is another shift that is happening, and has already happened for Mac users - the idea of supporting ideals with purchases. Apple has sold the idea of - pay for our quality, get a quality of life improvement. While I don't support that idea specifically (I like Apple's design, but don't support the company) I think that the trends of "Green" and "Healthy" and "Not Evil" are starting to move into the computer realm.
I don't think it's enough that games work in WINE, it's a company statement -- "We support your choice, we are cross platform". It's a win / win, and I support (with money) companies that take steps to have their software and hardware cross platform compatible. Most recently I started playing Savage 2 which was released for free; after playing a few days, I purchased the Prime account to give them some support.>br>
I, like others, have started to support my ideals with my money. I realized a few years ago that you have to "vote" with money, and now a year ago I realized that my support of companies that have green practices, of organic and local farms, of companies that make clear public statements in favor of human rights made me a hypocrite if I did not support the companies that encouraged cross platform choice. I use linux as my sole OS now, buy RoHS complient electronics, and vote for technology that supports my ideals.
All this rant is really just to say that the trend is here, and companies should make an effort to make their current platform OS independent, or make their next engine or platform OS independent.
If you want to see game companies developing natively for *nix, get more people using it. The developers will follow, seriously.
Hasn't that been the chicken and egg / catch 22 problem since the year of linux? It's a terrible stance for developers to take. Think about it (here it comes) - how would that work with religion? Convert for support? Get more followers, then we'll pay attention? Change other's minds, and we like you, nuts to you if you don't. I guess it works that way already, and it's caused a mess. Why not take a stance of: we're accepting of your choice. Inclusive vs exclusive.