If this pans out, it will be the first time a US carrier has offered anything like this. From this screenshot leaked by BGR, it appears that these new plans will include something called FlexPay, which will let you buy your mobile device and may for it in monthly installments instead of upfront. It appears that you would still have a bulk initial payment (perhaps a set percentage), then the rest would be divided up monthly on your bill. This would obviously let people buy the higher-end phones without worrying about the upfront cost of the device. This could force the other big carriers to offer something similar, and could be great news for PPC users since they typically have the most expensive devices!
See more screenshots and information at BGR.