So far all our worlds are flat. That makes the earth unrealistic, as the region near the poles are streched, to an extant that Greenland is represented as big as Africa. With the transformation to hex shape tiles, I think a truely ball shape world is possible. Not all tiles have to be hex, some are pentagon, some square could be possible.

If you can't envision what I am talking about, look at a football (soccer), that will give you an idea.

The word you're looking for is "globe".

There's another thread that goes in depth about this.

But I agree, it will be possible. The problem arises about the pentagons, and where they will have to appear. Might be beneficial or negative to have a city there if its on land, etc...as I said, there's another thread made.

http://forums.civfanatics.com/showthread.php?t=354175