Based on an assumption of 0.025% growth in monthly deliveries, I am projecting Tesla to reach the 200,000 US delivery milestone in May of 2018.
Hold this date for a moment while I switch the topic to the Fed Tax Credit--
Per IRS Code 30D, the Fed Credit phase-out begins two quarters after the quarter in which at least 200k cars have been sold (in Tesla's recognition, sold means delivered to customer's hands). During those two quarters starting with the quarter when the 200k milestone was achieved, Tesla has an open ceiling to deliver as many cars as they can and those cars post-200k will fall under the full credit umbrella. After those two quarters, phase-out begins. [ https://forums.teslamotors.com/forum/forums/how-tesla-will-be-able-get-f... ]
To maximize the delivery volume under this "2 Quarters umbrella", Tesla must time the 200k marker at the first week (or even first day if possible) of the Quarter, then it has freedom to deliver as many as possible on the remainder of the Quarter plus the next, equivalent to 23 weeks of deliveries at full credit, as much as Tesla can achieve to deliver on top of the 200k already reached.
The first day of the Quarters in 2018 are Jan 1, Apr 1, Jul 1, Oct 1. The 200k projection above is estimated at May 2018, so this “marker” has already eaten time into Q2 (Apr - Jun). Tesla either has to adjust the delivery timing of the 200k milestone out to to Jul 1, 2018 (Q3 2018) or accelerate production and deliveries in order for the 200k milestone to hit April 1, 2018 (Q2 2018). July 1 targeting requires throttling back US deliveries (stockpiling), and April 1 targeting requires pushing capacity faster. The other option is to stay on present velocity and route inventory to EU and/or APAC, enough to offset and delay the 200k US milestone until July 1 (but filling the non-US markets in return).
Tesla can also chose to disregard the Fed Credit maximization and just go full steam ahead, letting the 200k delivery milestone fall where it may. If it lands mid-quarter, it will be a difference of two or three months worth of customer's deliveries who may not get the 100% of $7500 (but they’ll slide into the 50% of credit).
I am betting that Tesla will streamline the US velocity (benefitting EU/APAC) in favor of maximizing the Fed Tax Credit for US customers and will target July 1, 2018 (Q3 2018) to be the 200k milestone. This will set the phase-out to begin Jan 2019. Tesla has all of 2017 and 2018 to give US customers the potential of the full $7500 Fed Credit.
The product mix is another question.
Of course, if Elon opens another plant or goes exponential in expanding the Fremont factory, all bets are off.