T-Mobile's Uncarrier 12 is called T-Mobile ONE. The intiative brings back truly unlimited data, though there are some restrictions. Video can only be streamed at 480p unless you pay $25 per month, and mobile hotspot is free but limited to 2G unless you pay $15 per month.
T-Mobile has scheduled their next Uncarrier announcement for June 6th. It's Uncarrier 11, and rumors say T-Mobile will introduce a program that will hook T-Mobile customers up with free stuff every month.