Far be it from me to tell another person how to spend their money. With that said, going deeper in debt for a camera isn't a good idea. If it is your business and you can write it off or depreciate it as a business asset, adding more debt to what you already have wouldn't be a grand idea. I very much want a newer vehicle. However, my 11 year old Honda Pilot still runs great. The cushioning in the seats are horrible, it has none of the modern safety gizmos like back up camera, blind spot indicators and the like. However, I cannot justify a new car when the one I have still runs good. There are plenty of spreadsheets out there that will amortize a loan out and you can see exactly what that $7,000 will cost you over the life of your loan at a given interest rate. If photography is your business then it is just another business expense. If, like most of us, it is a hobby, you should consider the real cost of the purchase.
Z9, from friends who have one, is a great camera. I'm sure the Z8 or whatever it will be will also be a great camera. Only you can answer the question of if the total cost of ownership (loan plus interest, plus any other accessories you will end up buying) is worth the investment or not.
Jeff