It's certainly possible that it is a skyhawk.  The photo TimW put up doesn't look anything like what was seen in the Trailere.  But it maybe too soon to tell.  And that photo may not even be an officially published conceptual image of the skyhawk.  Afterall, lot's of people have been doing fan-based concept art for the various ships and characters in Halo since the original game.

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Finis Coronat Opus! - "The End Crowns the Work!"

"Seek freedom and you shall be enslaved by your desires. Seek discipline and there you shall find your liberty." - Bene Gesserit Precept, Chapterhouse: Dune