If you are on the list for a Tesla Model 3, your wait could be anywhere from a few months, to possibly over a year.

Tesla is now posting estimated delivery times for reservations. If you have a reservation, you login to your account and click on the Delivery Estimator.

Some people have decided to sell their Model 3 reservation and make some money. For what was a $1000 reservation, some people are listing for $2500 or more.
You can see on CraigsList some of the listings in the Los Angeles area.

Tesla is also promoting the used Tesla Model S as an option for those who do not want to wait.