Tesla needs to announce them far in advance so they get funding. They can’t just create another Model, start mass production and delivery without anyone noticing and caring to post it online. So they capitalize on the hype and sell as man as they can.
Furthermore there is no Tesla Model 3 from any other company. There is not even a Model S or X from any company. There are some products that are close but lack some desirable features such as being purely electric or being “techy”. For the Model X there is the Volvo XC 90 plug-in with 19 miles of range which wouldn’t get many people to work in the winter. The screen is a bit Tesla like but from what I have heard is that Tesla’s screen (and infotainment system) is much better.
For the Model 3, the only true competitors are the i3 and Chevy Bolt. The i3 is selling ok but does not have a lot of range and is a small vehicle. For its price, it is not really a good deal unless you are looking for any ev. The Bolt is a much better choice but many do not like its style. It is also not really available because it is often seen as a complicance vehicle. I have heard that people were laughed out of the store when they wanted to buy it. It is also not available in Norway where it is anticipated the most. My guess is that the 2018 Nissan Leaf will be the best choice this year but compared to a Model 3 still a compromise because it lacks (amongst all non Tesla) a proper quick charging network.
So the real question should be: when will the other manufactures start delivering?
More like the Chevy Bolt / Opel Ampera e, the i3 has very limited range while the Chevy/Opel offers between 300 and 500km of range thanks to its much bigger 60kWh battery. The BMW i3 only has a 33kWh battery in the newer version, previous one was even less than that... The Leaf 2018 goes in the right direction, but 40kWh is still no enough to do 3h+ road trips.
Also, you make a very good point by saying that the Chevy Bolt/Opel Ampera E is a much better choice (ignoring the design). Same pricing as the Model 3 but the range seems much better. Given the experience of Chevy, I think that they can reduce the price and mass produce the Bolt much faster than Tesla can do with the model 3.
The Nissan Leaf isn't new in 2018, it's been around since 2011 and is (I think) still the most popular pure electric car. I'm aware that the 2018 should have some significant improvements, but I'm confused why you don't count either the current models or the 2018 as a competitor to the Model 3?
Side note: if you know anyone with a Tesla and are in the Bay Area, owners can take three friends with them on a tour of the factory. It's fantastic and I highly recommend it.
The "old" Tesla factory was bought from a joint GM-Toyota venture that achieved average production of 25 000 vehicles per month running those lines for 25 years. Then that venture failed, Tesla bought the factory and repurposed the existing infrastructure.
It's like if SpaceX started by buying an old working NASA rocket design and repurposed it for the Falcon, but for Falcon Heavy they started entirely from scratch developing rocket fuels, engines, materials etc. without ever having done so before.
How much further can they ramp up? That is the pertinent question.
Model 3 production is way behind and currently does not look like it progressing. Musk is blaming Panasonic on the problems with batteries, while reports from the Model 3 factory tell about a lot of manual work.
So yes it is easier to announce a Pickup some years ahead than fix Model 3 production.