I mean, while I don’t agree that she has no plot relevance whatsoever, for a series called the Legend of Zelda, she’s not as plot relevant as you’d think she would be. Having her step into a role on more equal footing with Link would be nice, or even take center stage in some instances.
I will say that the footage we saw is rather limited. Playable Zelda isn't entirely ruled out, despite the trailer showing her falling into a hole. Especially since we don't know where in the game that is.
That said, I don't expect playable Zelda anyway.