I have my fingers crossed for a spherical map, but I'm not sure if they'd go ahead with it.
As others have mentioned, if you look closely at the spheres made of hexagons, there are always pentagons in them. Not even just a few, but a significant number of them.
Here's a sphere of pentagons and hexagons "rolled out" and flattened, and you can see just how many hexagons are needed for this.
In order to have a truly spherical map composed primarily of hexagons, you'd need to toss in these pentagons. There are several issues with this.
1. Hexagons only have 5 sides, and therefore 5 ways to move. This makes some tiles in the game different than other ones, which changes the strategy for that set of tiles.
2. Without a clear indicator that this tile is different, casual players might not understand why they can't move "up" from this tile.
3. Art. You'd need to redo a lot of the art to support pentagon tiles, as well as hexagons. Even then, it would still look weird.