Personally I would like the last flight to be from LAS direct to NCL but I think the chances of that are pretty slim. Seattle would be good as an homage to Boeing and its legacy. I think it needs to be somewhere other than JFK if only because those flights are exceptionally short and it's hardly worth bothering with
Maybe HKG or LAX? Either way I would definitely want to be aboard. Much as the Mid-J variant is past its best it's still iconic and I love flying out of places such as LAS and PHX on the 747.