There are a few diehards still out there, but not very many. Most have live shows with lots of SFX and the talent likes the convenience of using the carts. I saw a photo in one of the trade magazines, just last week, of a newly renovated studio that had a cart machine in view.
Cart machines were already on their way out in 1991 when Radio Systems introduced the last newly designed machine to be produced. Within a few years, RS and most others had stopped production having sold almost no more of them. The last cart machine I bought for any station was in 1988, I think. I have about 10 or 20 blue Capitol carts in storage along with an antique Gates Criterion (stereo) cart machine and a Teac 10" reel-to-reel and a couple of Panasonic direct drive turntables. None of it has been powered up in well over a decade.