I would love to see the next EU game, Stellaris or Vicky getting Chinese localization, but for I:R it would be a waste of effort to add Chinese support because, well, it's not a historical period Chinese players are interested in.
I run a small Chinese pdx games community personally (sized 260, most of them playing on steam - stop calling us pirates), and constantly translating PDXCON info on major chinese gaming forums, so I think I'm qualified to draw some conclution. In China people were chanting "Vicky 3" prior to the announcement day, on that day, crowds who were disappointed by not getting vicky 3 is much larger than those who felt excited about I:R. Chinese players arent interested in the era of rise of Rome, especially after confirming that the map excludes China, and the time frame wont cover the decline of rome (which is an era they generally have more interest in).
The conclusion is that unless you decided to add China on the map, whether as DLC or in vanilla, supporting Chinese language wont attract a substantial chinese player base to buy the game.