[SoftTalker]

I'd guess they'll continue in cargo service for many more years, just as the DC10 and MD11 did (despite the grounding after the Louisville crash, I expect they will fly again before finally being retired).

[loeg]

Fedex continues to fly the MD11; UPS retired their fleet.

[topspin]

Yes. There are recently built 747-8's that will in service for a couple more decades.