I would be shocked if any plasma screen produced now does not. Progressive scan has been around for many years now. Its very simple to check. Change the setting on the DVD, either the screen can display the signal or it cant. The DVD player will revert make to interlaced in 30 secs if it cant.
Hard for me to say as I had/have a 100Hz crt and it looked better allowing the TV to do the conversion and feeding it the interlaced signal from the DVD. The crt would go back to 50 HZ if fed a progressive scan signal and that looked worse to me.
Rather get a decent up scaling dvd or better yet go HD than a model with just progressive scan.
Progressive scan adds a little bit of quality, which is noticeable on a CRT far more than on most LCD's or plasma's. I tested this on my LCD monitor and progressive is a little sharper than non progressive. But that is about it.
Since the new tv's have a higher resolution than what dvd offers, you still end up with a blocky ugly picture.
An upconverting dvd will look much better, or if you can and want to, go Blu-ray.