There is a good chance that Amazon will become a MVNO like Wal-Mart, Kroger or Tesco Mobile in the UK.
Free Amazon kphone with a 2 years contract: $45 a month for unlimited talk, text, and 2GB of data.
After 2 years, you get another free kphone by sending in the old phone.
Probably a MVNO of T-Mobile or Sprint or both. I don't think AT&T and Verizon would go for it.