It seems supprising they would not incorporate blended winglets into the A380
Jhurditch, I think its far more likely that Airbus have held back on offering winglets at this stage, as the A380 is currently in a class of its own. They don't need to offer winglets to sell them. In a few years time, when orders start slacking, they can offer winglets as a very obvious differentiator between 'old' and 'new' A380s (think of the 747-300 and 747-400), to get the original launch customers reaching for their chequebooks again, so their fleets will continue to look 'modern'.
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
Jetstream Rider, I can't see how a wing extending to the edge of the 80m box without a winglet is going to be more efficient that a wing with a winglet of which the tip also reaches the edge of the box. If it were the case you wouldn't see them on 15 metre sailplanes.