I mean, I can't comment on the actual Phoenix design, but we know the X-Men in the film have comic accurate designs from the Frank Quitley designs, which is great. While I still prefer the ones from X-Men: First Class, it's nice to see the "main team" in comic accurate costumes.
As for Phoenix, I doubt we'll see her in her "traditional" comic design. With that said if the design in the EW cover is what they can pull off the whole time she is in Phoenix mode and in motion (and I know that is a big
if given some the spotty CG in this franchise), then the artfulness of the design might be one of the very best elements of this oddity.