Yes, there will be demos of Fallout: Wasteland Warfare at Spiel in Essen at the Modiphius stand. Modiphius will have two stands this year - Fallout: Wasteland Warfare will be at both in Hall 2 at Stand 2D109 and Hall 6 at Stand 6A118.
I've played the Demo in Essen and it was really fun! There where no new Infos released, but the Minis where much better painted than at Gencon. I only wished the Demo would be more complex then just 'kill them all!'