More to the point, 18F is supposed to be a self-funded organization that shouldn't draw much from the overall GSA budget. (Not sure if that applies to standing up the organization / hiring and other investments). It would be a hard argument to kill it. That said, The US Digital Service is out of the White House Office of Science Technology Policy (a distinctly political / appointed office) and USDS / 18F interact quite a bit so momentum could be a challenge if there was executive-level antipathy.