Donovan is a great player and is only going to get better. He probably would have benefited from a few developmental years to start his career with lower expectations but instead the team tried to remain competitive each year. The team gambled and made too many "win-now" moves that put more pressure on him and took away options from the team now.
He will evolve into a better passer, decision-maker, and defender. He will learn to limit some of his current mistakes and will evolve into a better leader. Ultimately he will be a top 15-20 player in this league, perhaps even top-10 (which is hard to do at his size).
The question is what team will he be playing for. Frankly, with Riley, Spoelstra, and their current roster, the "Heat culture" would probably be the perfect place for him to take that next step.
If I were the Jazz, I would be looking a lot at the 2000-era 76ers as the blueprint. Bring in a new coach to push Donovan's development and surround him with size, toughness, and defense.