Will my supervisor be contacted by a conference if my submission is rejected or requires revison?
Some conference systems do, and some systems don't. If the system contacted all authors upon submission, one could speculate that it will also do this when a decision on the paper has been made. But it really depends on the system, and as there are so many, it's hard to predict.

But I'm going to add that it shouldn't matter: Whatever the outcome, you will have to tell your coauthors one way or the other. If they learn it from an automated email, then that is as good as if you sent them a personal email.