787-9 is probably too much for the route. They're probably waiting for delivery of the 787-8
(I know I've said this in the past, but now it seems almost confirmed)
Extremely possible.
Do you have any indication that the 787-8 is on its way? I recall they had ordered 4 of those, but with the option to upgrade them to 787-9 as long as the production had not started.
For example in Q3 they said they decided to lease a -9 instead of the -8 planned originally