Becoming independent from China != completely severing ties with China. Also, I think these days a better served purpose of HK is as the access point to the whole Asian/SEA region, rather than the access point to China alone.
Also, HK seems to be (from an outsider perspective) one of the most (if not the most) "westernized" cities in the region, with the proliferation of English language and all, so I can totally see it becoming the central hub in the Asian/SEA region for a lot of companies from the west.