I agree the Delta SXM flight always leaves from terminal 4 but there might still be gate changes because we had a bit of snow here. We have logged entirely 2 many miles out of JFK to be surprised by anything. Get the Delta app for your phone and stay on top of any changes. Either way in or out of terminal 2/4 Delta provides a shuttle between terminal 2 & 4 so it will be much easier for you to make your connection. Any gate agent should be able to direct you to the shuttle.