How long will the skyscrapers last? Look at the Tsjernobyl sarcophagus, meant to be very durable: 20 years later it needs urgent repairs or it will fall apart. (though admittedly, that's no skyscraper
)
I'm really doubting any skyscraper will last 500 years, even if it's left alone. And the gothic church will just stand beside and laugh
Besides, modern architecture is all about how much you're going to reinforce the concrete. There's no art in that (though some modern buildings are very beautiful.)
