> I would have to imagine that the newer 747-8 would have the much lower pressurization

Two small corrections:

1) If it would have had a change in internal pressurization, the -8 would have a higher pressurization to allow for a lower cabin altitude pressure.

2) The -8 does not have a higher pressurization, because they did not change the fuselage construction. Newer airplanes have lower cabin-altitudes thanks to the use of composite materials, allowing for better fatigue properties.