You can still buy a 4:3 TV, and you can still get one that is merely NTSC (i.e., 480i), but has a digital tuner built in. These tend to be very cheap. If you doubt this, go to your local Best Buy and ask for a TV that costs less than $100, and say you don't care about HD.
As for the releases, I don't know why so many DVDs these days are released in 4:3 format when the film was made as a widescreen film. Perhaps it has something to do with Blu-Ray, because it could be that they now think that if you care about your films and have an HDTV, you are buying Blu-Ray discs instead of DVDs. That, however, is just a spur-of-the-moment guess, not a well thought out guess.