Of course they could, but chances are they won't. Most of the major financial decisions need to pass through congress first. Remember, it's not a dictatorship. As crappy as both candidates are, I don't think the country is in peril with either of them in office... not anymore than Obama that is.
I don't think the reaction will be as large if Clinton wins for a few reasons:
1. She is expected to win. Even Trump supporters have to know that by now, won't be as shocking.
2. She is a politician. She does what other politicians do... she learnt everything she knows from politicians. What's right and what's wrong.
Although she has some shit on her heals, she isn't a murderer and vote rigger like some people think she is and most people know that inside.