Yes, this is possible in context, if you want to make a particular point.
Normally you would say "I'll study unit 20 tomorrow". This is unmarked, it makes a simple statement about the future. This might be a plan or a prediction.
However, if you want to emphasise the strict inflexibility of the schedule, you may use the simple present, with a time expression like "tomorrow". This is marked, it makes a particular point. So don't use it unless you are making the point that the timetable cannot be changed.
It would be unusual in your context, since you have decided to study one unit a day, and I would expect that you are able to change your mind, so the timetable can be changed.