Considering we still know very little about the characters or plot, I'm not gonna jump to any sort of kneekerk reaction, here (beyond 'I like what I see so far'). That comic above could apply equally well to Neo and Morpheus (minus 99.9% of the sexual tension). 'The mentor and the chosen one' is a storytelling trope how many thousand years old? We have zero data so far to indicate Rey does any more for Finn than give him a hand up when the First Order is carpet-bombing, presumably looking for him/to kill him, and gives him a lift out of there. Either she knows some Resistance folks or they run into same, or otherwise through various script contortions he ends up getting mentored by Luke. Not Rey. And since he was already a stormtrooper, and she a fringer, I'm willing to be he's a more-highly-traind fighter than she.
I honestly hadn't thought at all about skin color or gender until other people commented (usually negatively). They were just... the actors cast. I was curious to see their respective character arcs, however deep or shallow those arcs may ultimately be over the film and the triogy (and beyond). When Finn popped up in the first teaser, the first thing I noticed? Stormtrooper-like armor. The second thing? Probe droid noises. It wasn't until people online started saying how he had to be in disguise cuz there aren't any black stormtroopers and stuff like that that his skin color in any way crossed my radar. I mean, I'd noticed, yes, but I hadn't noticed -- like I'll notice you've got brown hair or green eyes. It's just a datum that gets filed in case it becomes relevant later.
Likewise, I don't automatically assume anyone is or isn't a main character (although I think smart money's on Finn, because Jedi). Rey wil probably have a more well-rounded character and role than Leia or Padme, due to 1) different era and 2) George Lucas isn't writing her. Padme did okay in TPM, but then the whole love story/forbidden romance thing got smeared all over AOTC and ROTS and she did little but angst in those other two films. As long as Rey gets better than than, I'll be happy. And from the examples we're seeing in Clone Wars (Ahsoka) and Rebels (Hera and Sabine), I'm optimistic. Which reminds me of a sidebar on the matter of unthnking sexism. Can we stop calling strong, competent girls/women "spunky", "sassy", "feisty", "tomboy", or other words that 1) would not be used for boys/men and 2) indicate they are somehow "not actling like normal girls/women". I ground my teeth when I saw all those labels being applied to Sabine...
--Jonah