While the extra two stops of DR can probably help, I wouldn't say that its solely enough to capture the full dynamic range of a sunset. It would really depend on exactly when you took the shot...however when the sun is still above the horizon, even if its partially obscured by clouds, the dynamic range of the scene could be as much as 18 stops, probably much more with a naked sun. With the sun below the horizon, things are a little more manageable. I've found myself having to use three stops of hard graduated ND filtration on my old Canon 450D (10.3 stops of DR) to properly balance out a scene, and even that was pushing it, keeping shadows a bit too dark.
I would figure an average sunset is probably 14-18 stops of dynamic range, depending on the exact scene. A Nikon with 13.7 stops of DR might be able to handle it in RAW, but you would have to perfectly tune exposure and use up every last ounce of capability the sensor had at the best ISO setting possible for maximizing DR. Realistically, its very difficult to actually utilize ALL of the DR available in a DSLR. Assuming no tone curve is applied to the image (or in other words a linear tone curve), you might be able to make better use of the DR that is available, however the final results wouldn't look all that great. The scene would lack contrast and appear rather dull. Factoring in about a stop of DR on either end of the tone curve to add some necessary contrast, and the 14 stops of the Nikon drops to around 12 stops, and the 11-12 stops of a Canon drops to around 9-10.
Realistically, your probably going to need some GND filtration on either camera to really capture a full sunset from dark shadows to bright sunlit clouds in a single shot. A very bright sunset sky with a naked sun is going to be difficult regardless of the circumstances, and GND filtration or HDR is going to be a necessity (unless you opt for silhouetted foreground.)