The first image of the box for the new Lego Nexo Knights 70317 The Fortrex has been found. This description is taken from The Toy Insider website.
"The Fortrex is a huge two-in-one rolling castle with more than 1100 pieces. Kids can launch the Knight Cycle and Aero-Striker V1 to engage the Ash Attacker and Scurriers! Fold out the walls to reveal the hi-tech HQ and get your brief from Merlok 2.0, and plan your next daring mission at the round table to stop Jestro taking the Book of Evil! The set includes five scannable shields for NEXO Powers: Ground Power, Super Human Speed, Hawk Holler, Chicken Power and Charging Attack."