Two viewings in, I really can't put it any better than this: I think she's Luke's daughter, all the pieces are there for her to be Luke's daughter via any number of explanations. If she isn't Luke's daughter I will be truly surprised. So I won't be disappointed if she is, but it's legitimately exciting to consider the possibility that she's not.
If all of the hints thus far are in service of a red herring, then I bit down on that herring hard and am being reeled in.
This trailer will, frankly, be an enormous misdirect if no new characters are revealed to be related to Luke Skywalker.
Then again, if the eventuality comes to pass that Luke adopts a wholly unrelated Rey as his daughter... the repurposing of those lines from Jedi will actually be even more powerful.
...I got goosebumps while typing that, lol
The idea of family being a larger concept than blood ties is a solid one for me. Honestly, I like the idea of Luke coming to love her as a daughter over the course of her training. Think of it from Luke's perspective: he loses what he sees as the next generation of his bloodline and his legacy in the force to the dark side. He's broken and alone on this planet, searching desperately for something that might not even exist.
And then in walks this girl who won't take no for an answer, who is brilliant and optimistic and just...she's him when he was a young man. Slowly, she takes up a place in the old man's heart he thought would sit empty forevermore. She learns the ways of the Force from him and exceeds him, defeats his greatest failure, returns justice to the galaxy.
Yeah, blood or no, that would make you a proud father indeed. At that point, you earn the name Skywalker.
Like, it would be like how you can be a noble or you can be noble. Kylo being the first and Rey being the second.