If the Communists (PRC) control North China and the Nationalists (RoC) the South, Hong Kong will be turned over to the RoC (with whom, unlike in OTL, the UK will not break diplomatic relations in 1950) on schedule in 1997. (Yes, all of it--in the real world you can't separate the New Territories from the rest of Hong Kong.) Hong Kong will be as indefensible against a regime that controls half of China as against one that controls all of it.
By that point one in 1997, in that ATL one would hope the ROC would have turned their ship around, even if it starts off as a mega-Singapore at first. In that case HK either has nothing to worry about, or has SAR status (as per OTL), or becomes a special municipality (i.e. the same status IOTL as Taipei, Kaohsiung, and the most recent ones promoted from county status). Of course, to get the democratization ball rolling to a similar level as Taiwan's OTL would probably require a major scandal that means that the central government would have to do something to avoid embarrassment and the loss of face that would result.