They are. That's why they haven't been revealed. I mean, Sanderson could tell us how Rand will defeat the DO in the first chapter of the next book, but I doubt he will.

In a way knowing the Arthurian parallels makes for more rather than less uncertainty though because instead of being left to guess what the author will do you're left to guess IF the author will do it. Almost every character with more than two lines is a trope, so each of them is the lady or the tiger for the length of the series. The best example, to me, is Gawyn: Jordan practically tells us point blank he could take on the Lancelot role saving Guinevere from certain death--or do a complete 180° and kill her with his own hands. Egwene herself knows it if she stops to think about it 'cos she Dreamed it. I guess that's a mystery that's resolved now though. Of course, there are two more books....

EDIT: I hate when I do that....