It seems supprising they would not incorporate blended winglets into the A380
Airbus were constrained by an 80m "box" into which to fit the A380, that might have something to do with it. Having the last 5 m ish as winglet might have been less efficient than having wing all the way to the edge of the box. There is a lot to think about in wing design, but I wouldn't be surprised if the span limitation was the reason for not having them.