It's not as big of a risk as you imagine. There are 40 million native Mandarin speakers that do not live in the PRC and that number is increasing plus the billion or so inside China itself. I highly doubt they would ban Steam as it is willing to comply with nations and ban specific games in specific countries. It's all speculation regardless.Censorship remains all-pervading - in fact is getting worse - and sales portals like Steam exist in a legal grey-zone that means they could be shut in mainland China at any moment if the government decides to do so. Basically Paradox would be taking a big risk with limited pay-off.
Perhaps people from China could weigh in on the possibility of their country outright banning Steam in the near future?