[AnimalMuppet]

For your purposes, it doesn't matter. You can do your capstone in the current hotness, or not, as you please. If you do it in deep learning and in five years deep learning is passe, it won't matter. You'll have your degree and be four years into your career. Or you'll be four years into grad school. You'll be fine. (In this scenario, if your grad school is in deep learning, you won't be fine. Think harder about that choice than about your capstone.)

Given all that you've said, a capstone that tries to dent the "inscrutable nature" of deep learning might be an interesting choice.