So, why is this a potential spoiler? Many have speculated the new, young heroes featured in the build-up to the new film have familial ties to the heroes of the original trilogy -- the "I know your eyes," comment may allude that one of the characters in the trailer may be the offspring of Luke/Leia/Han/Chewie/Lando/Yoda (but probably either Luke, Han, or Leia), thus connecting the two trilogies and awaking the Force and all that other cinematic magic stuff.
When the line is spoken, the image of Han Solo fades into the characters Poe and Finn quickly embracing -- but, a shot quickly follows of the female lead, Rey, prominently featuring her (...wait for it!) eyes. Are you thinking what I'm thinking?