At 16" it would still put them at a barely noticeable 100g (at 2kg) and 0.6mm difference. Even after Apple rid itself of Ive's obsession with thinness they would never go for "significantly thicker and heavier" than the previous model in a portable device.

Can't really think of many (any?) laptops that have this mix of thin, light, high performance, and long battery life.