Any ideas if the cargo variant has the same extended upper deck?
Yossar is correct.
This plane seats roughly 455 vs the A380 525 in 3 class standard configuration. Naturally, both can jam more people in with whatever interiors they choose to install.
The biggest difference is that no airport needs to be modified, or arranged for the 747 as the wingtips are not as big of an issue as with the A380.
Both are fine planes in their own respect, but other than Asia, the days of huge long haul aircraft are limited since most twin engine configurations are approved for over water flight, and the fact that no one wants to wait 1 hour to get de-planed or boarding at an airport.
Boeing pumped this out because the R&D was next to nothing (compared to the A380 which is rumored to be around $10 billion) and it fits that long haul, high passenger nitch that the A380 has had since its first delivery.