These photos were taken out in Los Angeles, presumably for some warm weather testing outside of Michigan. At the Silverado's debut, GM VP Mark Reuss said there would be a significant difference between the Silverado and Sierra with this new generation. The grille on the Sierra appears to be far more upright and rectangular, contrasting the rounded look of the new Silverado. The headlights are larger and more upright. The same goes for the foglights. The profile and rear look fairly similar, though the fenders on the Sierra are more squared off.
While we don't know what will rest under the Sierra's hood, expect it to share powertrains with the Silverado. That would mean updated versions of the 5.3-liter V8 and 6.2-liter V8 would be joined by 3.0-liter inline-six diesel. Look for the new Sierra as soon as the Chicago Auto Show next month.