Still think they could include a stronger narrative while keeping the sandbox bit accessible and fun. Most important is the inclusion of enemies with special powers, and it seems as if that is already a lock.
I would like to see some refinement to the way the character moves. Nothing that changes the fundamentals of the moveset, but something to make the transitions and moves feel more natural. Automatic leaps over small obstacles, more twists and turns, and so forth.
Mentioned this elsewhere, but chain jumps would also be neat.