Mainly I've been reading replies about Sora not being a light, i believe he is. Near the end of DDD , Mickey and MX were disputing between the 13 darknesses and 7 lights. mickey mentions the names Himself, Riku and Sora and his three missing friends( Aqua,Ventus,Terra). That is 6, but Terra is still unknown if he is a darkness or not, and i know for a fact Aqua will be saved and Ventus will be awakened, so that leaves 5. But Lea and Kairi now we know can wield a keyblade may fill the two empty spots. Back to seven. And yes Sora is a guardian of light. It does say the lights consist only of people who originally possessed a keyblade, and Sora wasn't one. But Sora still proved himself worthy to be a light and to have a strong enough heart to be one. Though it was through Ven to wield one, Sora proved to seem like he was originally a keyblade wielder. Besides, if everyone is saying that he is just ordinary person and not meant to be a light, then why in the first place would Yen Sid put Sora through the mark of mastery exam to become a master of a keyblade? The way i see it, it was like Sora was meant to have a keyblade even if Riku didn't go into the darkness. Speaking of that, since the keyblade was meant for Riku but he went to the darkness, out of everyone, it chose the wielder to be Sora. That should make Sora a Light. Plus Riku got another keyblade (soul eater) making like the kingdom key originally for Sora.
So my opinion , the lights are : Aqua, Mickey, Riku, Sora, Ventus and now Kairi and Lea. unless Terra is saved somehow, then he would either take Kairi or Lea place.