This issue always causes confusion, because in other countries, admission to college is based on the predicted IB scores, and conditional on the final scores being sufficiently close to those scores. It is also my understanding that some US universities may use this procedure for international applicants who are IB students.
For students at high schools in the United States, this procedure is usually not followed. Rather, what matters for admission is letter grades, not IB scores, and the predicted score is irrelevant. Thus, typically, the final IB score will not matter UNLESS you want to use it for credit or acceleration. It is unusual for anybody to be rescinded, but it sometimes happens if the final semester letter grades are very low–and some colleges require certain prerequisites, so failing a course could also get you rescinded.
But it’s hard to be sure what any specific college does–there is no standard rule. The best thing to do is to call the college directly and ask them about it. And then try to do as well as you can on the IB exams.