SET 18,
You're probably right - except that freighters will probably keep the 747 line open for a while yet. There is lots of 747 infrastructure around the world - but getting 380F infrastructure set up is a bigger deal. It's not just loaders but ground infrastructure like taxiways & maint capability. Fine for hauling freight from Stansted to Shanghai, but if you wanted to drop into somewhere like Harcourt with a 380F you might have a problem. So the 74F line might have life for a while (unti lit gets eaten up by the 777F line. So the Big 'B' can piggy-back some cheap(ish) pax versions onto the line as the marginal costs aren't great - eg. same interior as 777, same engines as 787, so it's not as if you're having to inventory a whole lot of type-specific parts just in case, but can easily slot it into your supply chain.