When the Tesla rep called me a few weeks ago to confirm my order, he mentioned that the cars aren't necessarily built/shipped to order.
He explained that a number of each configuration is built and shipped for a specific market, and our choice of config will determine your waiting time.
He said that since mine is a blue/white LR with the 19" nova wheels, id likely see my car quite soomer than if id gone for stealth grey or ultra red - new colours are usually more popular, so the allocation gets eaten up pretty quickly.
Makes sense to me