saw this type of thread yesterday on gaf.
About the protagonist. To me the most logical thing is that the progatogist is sheik/Tetra (an alternative form of Zelda) I dunno I somehow connect Bow and Arrow with no sign of sword whatsoever to Zelda (thanks to TP)
Other possibilities are obviously the child thing you mentioned or its a silbling of Link like in WindWaker.
And since you have never been able to see one of link's parents what if this is a parent?
I mean we already know one link's grandmother. So seeing the world of his parents go down the pooper and having a war with whatever enemy comes up then parents dying or whatever and we get a "17 years later" screen and play as Link.
Off topic but I find it hilarious that so many people on the internet (not here) think its important to have grass like that on WiiU hello did you guys miss FarCry3?