My parents came to HK a couple of months before I did - in fact, I came to HK because my parents had been here a couple of months earlier, they'd stayed with my cousins-of-cousins here, I'd come up in conversation, and they ended up offering me a job...
They weren't particularly keen to come back - they felt they'd 'done' HK, so the only reason to come was to see me, and they tend to travel more in Europe and North America, plus they decided a while ago that if they were going to do long-haul, they weren't going to do economy class any more, so it becomes pretty expensive. We came to an arrangement that they pay for my flight to the UK once or twice a year, which is much cheaper for them...
They did visit, briefly, this year and last year, since they had things to do on this side of the planet - went to a cousin's wedding in Sydney last year, and cruised from HK to Mumbai this year. Last year, we did some sightseeing, I showed them around my neighbourhood, took them to Cheung Chau for a different side of HK, etc. This year they were only in town for a day or so before getting on the ship, so we didn't do much other than dinner.
I think it's fairly unlikely they'll ever come to HK again, unless I do something stupid like get married or have kids here