No firsthand experience with software sales in China. I'd welcome someone with detailed knowledge to chime in, but this seems like an area that is accepted as convention and one I'd challenge. Sure they'll ban it. But so what ?
I live in China, and from what I can see, the game is not marketed at all. I've had to use a VPN to purchase it. My Chinese friends download hacked Chinese language versions.
That being said, if we're worried about going against the worldview of the Chinese government (a more basic argument than 'pissing them off') they consider Mongolians to be a Chinese ethnicity. From what it appears, with FDI and border city projects, the PRC would like to absorb Mongolia, though I highly doubt it's a top priority.
I think it's still possible for another expansion. Based on the "if there's a good idea, we'll make Civ VI" POV, it seems more likely to be able to improve AI, mechanics, improve random events (which GEM has done, maybe the devs can officially work out disasters), and corporate entities (a lot of good ideas have been mentioned in these forums).
One clue I can see for Civ VI is that they want to work out a way to have a weighted tile occupation, based on unit types, instead of strictly one military unit per tile. I love this idea as a healthy compromise between the annoying navigation from OUPT and the stacks of doom.
I personally would like to see CS's keep conquered cities, instead of razing them (like in Civ Nights), and hostile CSes actually acting more aggressive (Venice anyone?).
What about incorporating a diagnostic tool in the main menu for pointing out conflicts with mods?