You do not have to trade an iPhone in to get iPhone forever. If you want the promotional lease rate of 15 per month, yes, you need to trade in a working smartphone. If you don't trade in, you will pay 22 a month for the device lease. IP forever means you can get the new iPhone each time a new one comes out. You turn in you current iPhone, which wipes out the current lease, and then start a new one with the new device. There is a purchase option. Example:get a 6S today, go back next October to get the ip7. You can either turn the 6S in which wipes it's lease out, or you can pay the remainder of the 6S lease off and still upgrade to the 7 while keeping the 6S. You do also have the option of not upgrading, and keeping the current device until it's paid off. Once your lease is paid in full, the charge comes off of your bill. It's very similar to the att next plan on most aspects.