Longer reach, reverse power, downloaded upgrades for the customer equipment, DTA over coax, and a dozen other improvements. The updated G.fast standard was pretty much agreed last week at an ITU SG-15 meeting in Geneva. The major chip vendors, Broadcom and Sckipio, are already hard at work. The carriers are hoping for equipment in the second half of 2017.
I have hundreds of pages of proposals from some very good engineers so this is just the first pass. Amendments one and two were approved. Amendment three was consented but very few changes are likely before final approval.
BT needs longer reach. Their finance guys insist they use existing cabinets rather than building to the distribution points closer to the customer. G.fast was designed for 50-200 meters but existing cabinets are often 350 meters away or more. The new standard increases the maximum transmit power up to +8 dBm, with a practical goal of 300 megabits 300 meters. See BT G.fast Musts: ~ 350 meters, 48/96 ports. I didn't (yet) see anything about more ports, perhaps because that was possible without any updates. Broadcom had promised 96 port systems in Q4 2016 using external vectoring engines but the schedule has slipped.
AT&T has been vocal they want a true gigabit to compete with cable, not "up to a gigabit." Comcast offers gigabit downstream in parts of Atlanta, Nashville, and Chicago, with Detroit scheduled next.