"A good few of those more recent 747 sales were the -8 Freighter. These are very popular with cargo lines."
There's good reason for this. The Big Twins are efficient at hauling Pax but that comes at cost of payload mass.
People will point out that a 777 has a lot more cubic feet of cargo capacity available than a fully-laden-with-pax A380 (or 747), but they neglect to mention that the A380 or 747 can actually haul more cargo mass in the same situation on long-haul flights (ie: the 777 is great if you're freighting fluffy pillows transoceanic)
4 engine aircraft simply have greater lifting muscle. That's not necessary on a long-thin passenger route but it's important if you're DHL and friends.