A rumor from Bloomberg suggests Sprint will sell the iPhone 5 with an unlimited data plan. The #3 wireless carrier in the US could use this plan to lure customers from competitors AT&T and Verizon Wireless. These two competing carriers already sell the iPhone with tiered data plans. If this rumor pans out, it'll leave T-Mobile as the one remaining US carrier without the iPhone. The absence of the iPhone on T-Mobile may not really matter as AT&T is in the process of buying the #4 wireless carrier.
Sprint, and the other wireless carriers, are expected to sell the iPhone 5 in mid-October. The next generation iPhone will likely be announced at Apple's annual Fall music event a few weeks before it goes on sale.