Luke Skywalker was famously absent for much of The Force Awakens, discussed in awed whispers and regretful recollections, only appearing silently in the final scene where Rey found him in exile, so there’s something quite cathartic about Hamill getting one of the first lines heard from Rian Johnson’s sequel. The actor stated at Star Wars Celebration that some of Episode VIII‘s dialogue will “make you forget all about ‘May the Force be with you’“ – and while this probably isn’t what he’s referring to, there’s definitely something very Star Wars-y about the line – simple yet grandiose. It’s also nicely vague enough to work in a trailer as an arc hint without giving any actual plot away.
As for what it means, that’s anyone’s guess: it’s obvious elaboration on Rey’s importance, most probably the balance of the Force or the Jedi, but as so little is known about the character’s backstory (or even her relationship to the Skywalker clan) it’s hard to make any real conclusions. Breaking from series tradition, Episode VIII will pick up directly where the last film left off, showing Luke and Rey’s fateful first conversation, so it is a fair guess the line would come from that sort of exchange.
It’s worth noting that Zeroh makes a big point about how this isn’t confirmed; he’s heard it from several sources over the past few weeks and after research believes there enough credence to those to report, but as with the simple existence of a trailer it is still a rumour. That said, the simple notion of getting some new footage that this rumour invokes is exciting, regardless of if the details wind up baseless.