In an impressive show of support, the post from the Stardock CEO asking for Ashes of the Singularity [Steam, GOG] Linux version requests has more posts than reviews on Steam.
The Steam post has 656 replies, with practically all of them requesting a Linux version. The game itself has only 555 reviews in total, which is taking into account the reviews that aren't counted towards the overall score.
Also, if they do a Linux version and you want to see it on GOG, you can vote for that too here.
I would imagine with this level of requests for a Linux version, that it will be done. It will be interesting to see what Stardock do here. If they decide not to, then it will really make me wonder what they were expecting. Getting more requests for the Linux port than the total reviews the game has, should hopefully open a few eyes at Stardock.
As always though, I urge you not to buy it until it is released for Linux. I've seen people say they have now purchased it, which is extremely silly since they could still decide not to. Hopefully that won't affect their Linux sales numbers too much at release. I already own it from some time ago as a gift from someone, but I will likely buy an extra copy or two if it does release for Linux for people I want to play with.
That's another point worth considering when porting to Linux. You're not just doing it for the people who say they will buy it, but the people they might convince to also pick it up, or the people they buy extra copies for.