Even though metaphysics is a fringe discipline, it should still be a part of philosophy's overall tenets. The beauty of philosophy is that there are infinite possibilities in regards to what can be studied, talked about and rationalized. Everyday people probably don't concern themselves with the differences between nihilism and existentialism. However, philsophy can take many forms and metaphysics should remain one of them.
Yes, metaphysics should continue to be a subset of philosophy, because the study of metaphysics is highly related to philosophy. It is important to study why we are here, what our purpose is, and how we function in the world. Metaphysics should continue to be studied, because we should know why we are exploring our world.
I believe metaphysics should be a subset of philosophy. This has been the tradition for quite some time and it should not change now. I don't see any real reason to change it. I think there are a lot of parallels in philosophy that directly connect to metaphysics. Metaphysics can be difficult to category, but that doesn't mean it's been categorized wrong.
Many people are involved in the study of metaphysics now and it has become it's own scientific field. It should no longer be included as a subset of philosophy because there are many scientific studies that back the claims made by those in the metaphysical field. It is time for metaphysics to move into the scientific realm.