First, let's consider metalanguage. The idea that there's some conception of language beyond language, doesn't make any sense. The "thing" behind language, is thought. Now trying to conceptualize thought is virtually impossible because you have to think to think about thinking (like that?). Now, studying and thinking about what kinds of thought generate language. Sure, but don't call it "metalanguage."
Next, meta-philosophy, that's like saying the philosophy of philosophy. First off, philosophy is a vague enough word as it is: love of learning. What is that? Why do we romanticize the idea? I think the term meta-philosophy was made up by a philosopher that wanted to get laid (aka sound smart).
There's a large variety of words that misuse the term "meta-," and I won't go into them all now let's just say that most often the words could be replaced by some other word or concept.
The exception: As I mentioned before I think the term metaphysics should still be used. Here's why: God exists (only using the term "exists" because of a lack of a term that fits better) outside the human plane of existence, and there's no better term to describe something that is beyond our concept of the physical universe. I've written a couple times about this topic on my blog and I've posted some on this topic at a philosophy forum.