Many of the 'new planes' are replacements for the tired old workhorses that will be sold off or passed off to Dragonair; therefore there will not be a huge increase in crewing requirements. And the new ones will not stay shiny for long due to the corrosive filth in the South China air.
Also, retirement age is now 65 and CX captains are a relatively young demographic, so don't anticipate stepping into 'old timers' shoes any time soon.
By all means come up for the interview practice. You sound intelligent enough to filter out the BS written on these fora. Some posts here regarding company culture and cost of living are 'spot on'.
Enjoy your paid holiday in HKG. I think you'll find that three days in this place is enough, unless you are being paid A Scale!