As a department we are committed to offering a wide variety of courses reflecting a number of periods and approaches to textual study. In order to do so we change our course offerings regularly. Talk with your advisor about the courses you think you might like to take over the next year or so; she or he can tell you who will be on leave, and whether the courses you are interested in will be offered.
In addition, pay attention to the prerequisites in the course descriptions. In the event of over-enrollment, the registrar will be instructed to take those students with the stated prerequisites. If you do not have them, it is unlikely you will get into a heavily enrolled course. Read through the English chapter of the course catalogue to familiarize yourself with the kinds of prerequisites upper-level courses require and plan your course work accordingly.