The diversity of opinions in this thread is entertaining, as always.
As a Model S owner for over 2 years, driven over 40K miles, as much as I love the car I placed a reservation for a 3 and plan on selling my S in (hopefully) 2 years time when I get my 3.
The S is a far bigger car than I have ever owned, and a bigger car than I need. It's a fantastic car, but I prefer a smaller car.
The 3, with options, will be a luxury car just in a smaller size. I'm sure there are some S and X features that will not be available on the 3. But I don't expect any of those missing features to be deal breakers for me. I don't haul around lots of people or huge items so the 3 seating and trunk is fine for me. The 3 will of course have options like a bigger battery for more range, Dual Motors, a high performance version, fancy seats, all the same Autopilot capabilities as the S and X, all kinds of options.
And I find the appearance of the 3 just as pleasing as the S, except I like the front end of the 3 more than the S. But I expect sometime in the next year or so, Tesla will revise the S front end to make it look more like the X and the 3.