Or it could simply be that Luke is super jaded about the whole thing and this line is said at the beginning of the film until Rey shows him that hope still remains and the Jedi are still needed and he renews his belief in what the Jedi can be, ultimately leading him out of his exile and into the conflict between the First Order and Resistance.
It's just a teaser, so hopefully when a trailer comes out we get more context.
Edited by StarkJunior