Tesla is well known for unveiling its cars well before they are available to buy. However the lower cost Tesla model 3 will not be available until 2017 at the very earliest.
Telsa will start taking pre-orders for model 3 starting March, 2016.
The batteries that would power the Model 3 currently cost about as much as the car is slated to. Tesla is building an enormous lithium-ion battery manufacturing facility in Nevada to make its own batteries for far less money — the "Gigafactory" mentioned in Musk's tweet.
SOURCES - CNBC