I don't see why they need to rush into the higher end. Let ARM chips prove themselves for consumer scale. Enterprise is going to be weary of the new tech and potential compatibility issues. Proving it in the consumer market makes far more sense, and they really get to flex the benefits in something like a macbook air. Fanless, silent, and huge battery life increases are really tangible upgrades.

A beefy chip in an MBP 16 will be exciting, and I'm sure they are working on that, but it will make far more sense once ARM is established in the "normal" consumer models.