If my senior grades slipped by a little, but mostly stayed the same, would IU revoke my acceptance?

I got accepted into Indiana University in the fall of 2010. My first semester grades were not as good as they usually are, but my acceptance letter didn't get revoked. I recently got my second semester grades and most of them are the same as first semester, but one or two dropped by half a letter grade. Will IU retract/revoke my acceptance letter?