From what I can see from pics and the vidoes:

1) They have a "trim" line that keeps the Profile stable now and allows some tuning.  This is much better the floating profile they had on the first wing.

2)  They changed the Outline and reduced the anheadral.  This should give it more power and make it more stable. 

3) Looks like they stiffened up the Boom Connection point.

I have not tried them yet, so this is just guessing from what I can see.

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Gunnar

Thanks Gunnar...I actually have the Duotone 2019 4.0 wing and I'm wondering if it's worth to buy the new one or to keep it one season more...