It's very possible Link could have some kind of companion(s). We could be surprised and find out that some Dark Link like figure is Link's companion and could explain the use of Link's cloak, you know kinda like how we had Ravio and Ravio's bracelet from ALBW. Just imagine how interesting it would be having a true Dark Link like figure as an ally, I mean, we already had Midna from TP who was kinda like Dark Zelda type figure.
Midna hid in Link's shadow, so I bet a Dark Link inspired companion would do something similar for a method of hiding, like hiding in the shadows of Link's cloak for example. That could explain the importance of Link's cloak and the return of actual magic.
The Dark Link inspired companion could have a similar sarcastic like personality like Midna, only in a masculine, twisted, shady kinda way, where he's all cryptic about things. Then, later, when Link accomplishes the main goal objective for him, he eventually betrays Link, when he has all that ever wanted, a certain threat killed and perished, and all power in the world. Then it's up to Link to go stop him. That interesting plot twist to have another situation where Link has to fight a companion of his like in PH, only this time, the companion actually betrays Link of his own free will of choice with no higher power as a cause. I think it would give Zelda U a very dark feel and high sense of emotion and passion. The game already looks like it could have a dark story. I can already imagine this game being rated T for Teen.
Though, unfortunately, Nintendo will find some way of having the same old usual Princess Zelda, Demise/Ganon, the Triforce, and having the game rated E 10+, yet again. *sigh*
That's never going to end is it? *sigh*