The statement in the E-mail about charges leads me to believe they will be not be charged, and recieve either the improved or the original in a couple weeks. Either way, really cool!!
My guess is they are simply getting the dev model for free (probably to get rid of them and not be wasteful), and if they want to order the consumer model when it launches, they have to place a new order. I would think if they meant otherwise, they would say "Your order will remain in processing until the final model is complete, however to compensate you for the extended wait, we will be sending you a developer model in the meantime at no charge."