I have no practical experience in product design, but theoretically
I believe that in the near future cars will come out in two main types:
those which are designed for long distance travelling and those
which are suitable for travelling in town.
The ones for travelling within the town boundaries or other short journeys
will be very slow like the very first cars that were introduced in the
market, perhaps slower. The others will be much faster.
The video in the link you’ve posted is interesting. It shows how in the
past they used to have a vision of the future that was somehow distorted
in accordance to the stereotypes of that period. As an example, I don’t
see how a three wheel car can be seen as an evolution of a four wheel
one. I might be wrong though; there may be some good reasons that I
haven’t thought about to utilise that feature in the automotive industry.
I’d be happy to debate about it.
I see what you mean but I find it highly improbable for the design to go only in 2 directions.
About he vehicles in the city, people who will own small city cars will want these vehicles to be able to go fast as well. If not, industry would constrain them to buy 2 cars.. and it's not very practical (costs for customer, parking spaces, traffic growth).
About the 3-wheel car, you don't have to look at it as an positive/negative evolutionary step compared to the 4-wheel cars.
It;s just a different type let's say. Some people may find it unstable or so -- but this is because they apply 4-wheel car physics to a 3-wheel car.
I think if you make a proper design for a 3-wheel, it can be very stable as well and also very practible. This is how I look at it. Its all in the design, the sector it is targeted on.