I need to know if Delta 100% always lands at and departs from Terminal 4 at JFK, or rather, I just need to know what if any are the odds of the nonstop to/from Berlin using Terminal 1 for some reason, because the Airtrain doesn't go to T1 at all right now due to construction and if the flight uses T1 I'll fly to an entirely different city because I don't want to use the shuttle bus (because I have a long complicated train trip in addition to Airtrain. With the T1 Airtrain stop closed you have to take a special shuttle bus to/from T8, where the Airtrain stop is open.) Delta website sort of implies they only use T4 but is unclear and I've definitely seen at other airports where you land in a completely different terminal than originally scheduled. (The vagueness is that the Delta site says their flights depart from T4, but then it says baggage claim is in T4 which would mean arrivals also use it.)

Delta's JFK info is at Travel Info > Airport Maps & Locations