Trump may not have excellent follow-through, although the conservative intellectual centers are working hard to fix that if there is a second, but he does mean what he says.
Trump said he would put in a Muslim Ban - done. He said he would appoint only pro-life judges to the Supreme Court - done, with disastrous consequences.
So, there is absolutely no reason to believe he won't do this, a critical step for full-on authoritarianism.
Be Afraid, be very afraid.