Mew d is one of those cards that's just always going to be good anyways though, like there's no specific reason just the way it is is good. I don't think it will lower by much (After a while anyways).
I'd say once the next pop set comes out, the price should drop to half it's original value. And then because of it's lack of use (less 2x weaknesses in the format), it should drop a little more next format.