Objects in motion tend to stay in motion unless acted upon by an outside force. Objects at rest tend to stay at rest unless acted upon by an outside force.
While there will be some change in the rankings as people who did poorly the first semester kick it up a gear and do better this time, as well as a few that did well the first semester, slack a bit and drop a few places, generally there probably won't be a SIGNIFICANT change in position for most of the people in your class. To assume that everyone that did poorly are suddenly going to develop A+ study habits and a solid grasp of the material is unreasonable. Some will, but many won't. Ditto the flip side... while there may be a few people that drop in standing because of either their lack of effort or the improved competition from those below them, I wouldn't count on there being a major change. Basically, it's enough to give hope for those who did poorly to put in a massive effort and change their position... but many won't.