Well, hopefully they can successfully translate from DirectX to OpenGL, because I don't know that Wine can handle DX10 or 11 that well, if at all. Which means GalCiv 3 could be truly Windows locked. I also wonder why developers insist on locking themselves into one platform like that when there are so many other eager gamers on other platform that would love to buy games like this. A Mac version (and Linux, too) should be a no-brainer at this point in time. Even iOS and Android should be possible; this kind of game is a natural for tablet interfaces.
Like many Mac/Linux users, I rely on Wine for a lot of my gaming, which is fine for older games. But I'm done dual-booting; I don't even have a bootcamp partition anymore. If Stardock doesn't release a Mac version of GalCiv 3, then I'll move on to other games. But I really, really hope they do. Endless Space was a nice try, but I'm still waiting for the perfect 4X space game to come along and fill the MoO-shaped void in my life.