It will be a cold day in hell (or VT) before one of the seniormost member of the US Senate (and Chair of the Senate Judiciary Committee, and seniormost member of the Appropriations Committee) -- Patrick Leahy, D-VT -- would allow the only direct service to his state to be terminated. I think you can rest easy on DCA-BTV for the time being.

Now, when Leahy retires or is carried out, I would start making other plans for that route...