I am planning to switch from DSLR to Medium Format digital when the ZD is available.

I think I prefer to buy the AFD+ZD digital back instead of the integrated ZD system mainly because the back is separate. This means that when future, higher megapixels digital back comes out, I can just upgrade the back, without having to replace the entire body, thus saving money and keeping up with MP.

Do you think the AFD+ZD back would be a wiser investment? Does anyone think the integrated ZD system has any advantages over the AFD+ZD back?