The lightsaber stuff is the big thing here. When I just talk to people in my daily life, THAT'S the big thing that makes most of them connect her to Luke. Even the other pretty obvious callbacks (mechanical aptitude, naturally gifted pilot from a young age, innate compassion for Droids, etc) could still maybe be brushed aside, possibly.
But having it be Luke and Anakin's old saber, which the film treats like a family heirloom to be passed down from one generation of Skywalker to another (and calls back to ANH, where it was also treated that way), and it now calling specifically to HER, and giving her visions all about the Skywalker family, except for one (which was of her own past), and hearing the voices of Luke and Anakin's old mentors calling out to her, and Maz's words, etc.
If she ISN'T connected to Luke, then it's hard to see all of this as anything more than deliberate trolling on JJ's part (the big OT fan that he is, I don't believe for a second that he didn't realize that by putting all of this stuff in the film, that lots of people in the audience were going to make that connection).
And as for it being "predictable," I couldn't care less. Doing a "twist," simply for the sake of doing one, or because some people cannot think that you cannot tell a good story without shoving one in there, is not good storytelling. Luke needing to train a Jedi student who's is also his long-last child, to confront her evil cousin who destroyed everything that he built the first time, adds a new wrinkle to these films that we've never seen before (whereas we've done the more traditional student/master thing TWICE already) and could be really compelling if done well.
And I'll take that over some nonsensical "twist" any day of the week.