The iPhone would be able to pull 800 MHz LTE once it is available. It won't be able to pull the 2500/2600MHz LTE though, and from information that is out there we know Chicago will probably have widespread 2500/2600 LTE first (and soon). I think that is why people are suggesting a tri-band phone.
I don't think the One- Mini or Moto X will be triband, but I maybe wrong. I would look in smart phone section and read there.