The website is going back and forth between the placeholders and the same old design page for me this morning. We assume that the load is slowing it down and also that employees etc are the first to get the AWD and P options.
It may take a couple of days or more until 3/31, -‘d April (I’m April 2) get the option. Non owners, who knows.
The ordering and delivering are two different issues.
Ordering will begin when Tesla has buttoned down the options, specifications and pricing.
Elon has mentioned his hopes for when these will be going down the assembly line, but also stated it depends a lot when they are able to get production up to around 5,000 model 3's a month. If the production ramp does not go as planned, then most likely the dual motors/interiors also will not go into production until production smooths out for what they are producing now. No need to add additonal production complexity until they get things running smoothly in Fremont and Gigafactory.
Elon knows that there is a large pent up demand for these upgrades, and wants to be able to count on the plants being able to deliver.