With Civ V about to come out, people are gonna be hunting for the old ones which are supposedly better. How hard would it be for GOG to get the rights to distribute the Civ games?
Railroads and Pirates can come too if they promise to behave.
Alpha Centauri might be even harder to get, and it might not sell so well.

Plus, they can get the free Railroads as a promo for the rest of the games. I would love this, will buy all Civ games right away. I've been playing them ever since Civ 2 Test of Time... Gotta love that game!

Mars, now!

2k are the publishers, at least these days. Don't think we have them, so it could be a while.
Could also theoretically make the deal with Firaxis (the devs), but we also don't have them.
So, to summarize: The odds of getting Civ are no greater, and no less, than pretty much every other game on the wishlist.

Firaxis seem to love their community. If you can get a hold of them, a deal wouldn't be too hard to work out.

According to wikipedia all rights are now with Take Two.