AndrewC: Why would they need to expand the HK servers? That is, if they even have servers in HK. Google routes search requests along its whole infrastructure, only the homepage differs.
Because it would be nowhere near as fast if it was all from one geographical location. Especially when you're trying to meet the demands of a vast country like China.
In order to do this legally they can't do it within China itself, obviously. So that means they're most likely going to sell up and move out of China altogether. They're going to need to provide an alternative nearby and apparently that means HK.