What alternative do you propose for them? emigrate now? By 2047 many things could change, maybe China would become more democratic, maybe it would be easier to build a floating city, maybe indeed China would agree to leave more autonomy. The long term plan for everyone is to die, but improving things in short term is still worth it.
Emigrate to where? Taiwan? Singapore? Other places with a vibrant Chinese community? By 2047 things could change for the worse. You're being overly optimistic when all signs hint that it's getting worse. They're too close to mainland with the PLA at their doorstep.
