Kayne West and U2 sound like an odd mix. Is rap a popular genre in Australia?Am not at Mariah fan, but it is sad that it is cancelled partially due to poor response.
If performers/singers can't draw a crowd to their concerts, then it only discourages other acts coming to Hong Kong as part of their world tours.
Madonna went to Japan, but not other countries in the Asia area or Australia.
U2 are about to tour Australia, NZ & Japan. They are selling out Telstra Stadium in Sydney (70,000 seats) twice, plus a third concert has been announced. They are also playing other cities in Australia because Aussies support (most) performers who take the time to travel so far to tour Australia.
Kanye West is support for U2 - not sure how good he will be.
So, if you want to see the big names in music (western music anyway), then it looks like you will have to go to Japan, Australia or further afield.