There is no doubt that Dak has room to improve. That's a given. Even the greats usually peaked several seasons into their careers. There is always more to learn and more refinement that can be done to technique.
The beauty of Dak's rookie year is that everything that set him apart from the typical rookie QB was MENTAL. He learned more, learned it faster, and applied it better than anybody transitioning from college in the modern era. This is where the comparisons to modern flash-in-the-pan QBs falls apart, because those guys almost invariably were 1-read-and-run college gimmicks. Dak isn't succeeding the way Vince Young, RG3, Tim Tebow or Colin Kaepernick did - he's making reads and going through progressions like a real NFL QB. Tim Tebow came from the same college offense as Dak (Dak's college HC was Tebow's college OC), but Tebow was never anything but a spread monkey who never learned to properly run a play from under center.
You also don't see Dak rattled by pressure in any sense - from taking hits, from game situations or from the media scrutiny of being the Cowboys starting QB. When guys who bust aren't stupid, it's usually because the pressure of the position gets to them in one way or another. Either they can't take the hits psychologically even when they can physically, or they go off the deep end off the field.
If Dak continues his approach of 2016 through 2017 and beyond, the sky's the limit for him.