LTE 66 is new to phones and networks; I don't expect widespread adoption until 2018 or so. Even then, LTE 66 was in the future tense when the Priv was designed and manufactured.
I meant that LTE 66 would be supported by most OEMs and carriers by then. Right now it's literally only the V20, and WIND and T-Mobile appear to be guinea pigging LTE 66 before the rest.