I did a lot of research on this topic last fall preparing for this past winter and then never ended up actually camping anywhere. Most of our Skiing is in PA, but I did find a few options. A small few of the PA resorts had lots where they charge you to stay overnight. One was $60 per night and was just a stone parking lot. But I also found it not too difficult to find open campgrounds within 20 minutes of most ski resorts. There are campgrounds that stay open all year but turn off their water. two summers ago we vacationed in Lake Placid and there were 3 campgrounds in teh Whiteface Mountain area that were year round, but again they shut off water.
I agree that it would be fun as long as it's not insane cold. We have a 3 year old that makes these type trips more challenging, but we will do it for sure. Also, dont count out state parks. Some of them will leave a small number of either rustic or electric only sites open year round. The majority do not (at least in PA) but there are some if you do some digging.