The scenery has changed quite a lot in 10 years, in GT4 Prologue the IFC skyscraper (the one Lara Croft and Batman jumped off) was still under construction and you could see the cranes at the top of it in the game. For GT4 they crudely edited the photo to make it look finished but not in it's final design. Also there have been loads of other changes both on the Hong Kong and Kowloon side which would look amazing in current / next gen.
However it's unfortunate that many of those historic large neon billboards have been removed after the companies they are for have shut or they have become too old and are dangerous to leave hanging. They have been replaced often with smaller LED or screen based ones which don't have the same effect.
I always wanted a larger track which would have you drive into the Cross Harbour Tunnel, drive along the Hong Kong waterfront, go into the Western Harbour Crossing Tunnel and come out at the ICC skyscraper then head back to Nathan Road. Hong Kong island would be just as spectacular to drive along the harbour front through Central.
As for Macau the Guia Circuit absolutely needs to be in Gran Turismo, it was in PGR and looked amazing.
This Ferrari advert gives a hint at what New York and Hong Kong could look like next gen