Earlier quoted context omitted.
The 787 replaced the 767 in Boeing's lineup, which in turn was competitor of the 350. The 747 is still incredibly successful for cargo, so the 380 didn't replace it; it is absolutely nuts that AirBus didn't come up with a cargo version of the 380 yet. Next up is the 777, which has higher capacity than the 787/350. However, it is modern enough that it can probably just be upgraded, no new plane is needed.
You can't just take the seats out and fill it with boxes? What else is needed for a cargo plane?
"The A380-F would be able to carry 60% more volume than the 747, but only 28% more weight."
https://www.flexport.com/blog/airbus-a380-no-cargo-equivalen...