Metro PCS, one of the smaller US carriers known for cheap prepaid plans, has already activated their LTE network in a few major cities. Currently they have one LTE phone available but it's a disappointing featurephone.
I'm sure a lot of people would be interested in unlocking one of Verizon's high-tech Android phone's to take advantage of Metro PCS' cheap prepaid plans. Once AT&T activates their LTE network, customers will have greater choice of carriers if LTE phones are capable of being unlocked.
Update: I looked at the specifications for Metro PCS' Samsung Craft LTE feature phone and Verizon's Pantech UML290 LTE data modem and it appears that they are using different frequencies. Metro PCS appears to be using 1700/2100mhz for their LTE network and Verizon is using 700mhz. I read that AT&T owns some bandwidth in the 700mhz range, so in the future, it may be possible to unlock a Verizon phone to work on AT&T and vice versa.