Has anyone heard anything about a replacement for the ND-BT1? I've heard a few rumblings that Pioneer is going to replace this module, although I have no idea what the changes will be.

I have not heard of such a thing. And I would also bet the problems we are having with bluetooth voice quality and such are not based in the module but in the Z1 itself. I think we would need software updates more than a new bluetooth module. But I could be wrong.