DSC is available for new caravans provided they are fitted or can be retro fitted with electric brakes. Most leading caravan manufacturers will offer sway control as a standard component, especially on larger caravans. You should definitely make it a part of your checklist when buying a new caravan to ensure the manufacture has or has not included a DSC as standard. If it has not been fitted you can request that it be done prior to purchase or choose to go to a certified installer post sale.
When you have DSC you have peace of mind that you have done the best you can to protect your investment, yourself, passengers and other road users. It will aid your resale and possible reduce your insurance premiums. So if your new van does not come with DSC insist that it be fitted.