Any downwash caused by the curvature of the wing is preceded by an upwash. Anyone done the maths to see how these might cancel each other out? The streamlines show no net downward movement of the air, so where is the lift for a 747?
Any acceleration imparted by the curvature of the wing would (if you ignore benoulli and think Newton) impart a downward force onto the wing itself as the centre of curvature (somewhere below the wing) is where that force must be trying to push towards (like centripetal force).
The air on the underside of the wing pushes the wing up.