Sprint has confirmed it will continue to offer unlimited data plans for the next iPhone it carries, even if the next handset supports LTE. That should be a big differentiator — neither AT&T or Verizon Wireless offer unlimited data plans anymore, and T-Mo has yet to get the iPhone — but Sprint somehow hasn’t been able to capitalize on it much, as my colleague Kevin Fitchard writes here. Sprint could probably acquire more subscribers if it stepped up its marketing game a little, but I’m guessing that a major reason it doesn’t claim more iPhone users is that most subscribers simply don’t use enough data to need an unlimited plan.