Julian,
Generally incorrect. If they release a new product before shipping whatever you ordered they will give you the new specs. Now it depends where you live as to how it exactly works.
Example if a reseller in europe orders kit and it is not delivered then the order is cancelled upon release and automatically added. Same thing goes on with end users to the Apple Store.
I'll bet strongly (if you have no shipping reprts at all yet) you will get the new model in about a week or so. Hey never second guess Apple though, nobody really knows when anything is due to ship, including Apple. You just sit tight and hope for the best.