I think a big upgrade in the pipeline has to do with the bargeboards, not so much the actual bargeboards but the vortex generators on the foot plate. Other teams have them but McLaren does not.
In fact by comparison McLaren's bargeboards are rather barren, although a big improvement over last year, especially in regards to use of surface area.
McLaren had the VG on the foot plate last year, and comparing this and last year's design of this area shows just how much more surface area is available now.