The overall shell height of the new seats actually appears to have been slightly lowered from the original style. The manual specifies that the child's head must be 1" below the top of the seat for rear-facing. If that's correct, the seat will likely not last to 40 pounds rear facing, perhaps not even the original 35.
However, if they are counting the adjustable headrest in shell height, the way they do with the Frontier, then the overall rear facing room will have increased sufficiently to make the 40 lb rear facing limit realistic.
Of course, I'm rather hopeful it's the latter