With the talk of Kai tak being possible, this is what I see being LIKELY ADDED (none of this is confirmed nor denied, same with Kai tak being not confirmed nor denied) :
A lot of new liveries for planes such as the b747, b757, a340, a330, a320, and a300 mainly in retor livery
Advanced 747 to account for the shear amoount of 200 and SP operations into the airport
A new way that approach works to account for the right turn on approach
About 4 to 5 plane Spotting cams within both the city and bay area
New planes consisting of the: md11, dc10, L101, 763, 742, 74SP, 742F, 744, 744f, MD11F, dc10F, a313, a30b4(if not out by then, model is complete and awaiting liveries and release) (others if any get updated model such as 748, 748i, 748f for modern airports)
Any extra M or S such as md80 series, etc. Might be there too
Unknown if modern arrivals will exist along with retro, though speculated by many they will
Concorde is also speculated to be regular at a premium because of retro time and the fact it did operate to Kai tak
More x size non-gate stands
Airlines such as pan am, mandarin, ansett Australia, and retro American, and united (Air China, Korean Air, Etc. Liveries haven’t changed)
MIND YOU THIS IS ALL SPECULATION FROM WHAT I’VE SEEN IN PLANE SPOTTING VIDEOS (that and just overall retro stuff)
AGAIN, MIGHT COME, MIGHT NOT, DO NOT COME TO ME WHEN SOMETHING ON THIS ISN’T ADDED
Most plane/airline facts were obtained through this video: Plane Spotting Memories from HONG KONG KAI TAK Airport (1995) - YouTube