Why Sora Is Still "The Chosen One" OR Please Shut Up about There Being Like Forty Keyblade Wielders

Oh, I thought you meant something different. Nvm. But anyway, yeah, I can see where you are coming from.

 

About the "Door to light" even though i do believe that it will be further explored, he already did open a Door to light that made he and Riku be able to come back to the realm of light, in KH II also he was able to escape the realm of darkness with the sweat salt ice cream that Riku gave him.
Most people that are trapped in the realm of darkness get stucked there until they give in to the darkness (and use dark corridors) , or use the help of some worlds in between like Castle Oblivion. For beings of light to escape darkness unharmed is pretty difficult, and Sora did at least two times, just by Seeing that Master Aqua is stuck in there for more than 10 years it goes to show how difficult is to escape without give in to the darkness (but she gets a golden star for not becoming a Heartless after so much time in there).