I'd say yes, at least a moderate number. It seems many are treating the Adventure as PART of the their holiday, rather then the whole holiday.
In the
Disney Adventure FB group (or one of them, there is probably multiple) the other day, someone put up a poll asking who was booked/planning a B2B vs a Single cruise.
40% said B2B
The comments from many of the people regardless of their vote shows people also planning to do a park add on or further exploration of the country.
Obviously the group isnt just Americans (i dont think there has been a poll or anything to show regional breakdown of members), however Americans also aren't the only ones who would have a long flight times.
The draw of a new and completely unique ship is also quiet strong.
I highly doubt there is alot of people going just for a 3 or 4 night cruise, but quite a decent number making the most of the time and money they have to spend travelling. When we get the chance to go, we will likely do a park and something exploring before a B2B.