Gigabit required to keep up with cable. It's in the standard, but until recently everyone assumed it would be delayed for lack of customer demand. But with gigabit cable coming close, AT&T is pressing for a gigabit over DSL. Adtran, a major supplier to AT&T and Deutsche Telekom, has proven that G.fast can easily exceed a gigabit downstream by bonding two lines. It's just a lab demonstration for now without a timetable for field trials.
G.fast vectoring and pre-coding require serious processing power to keep up with the high speeds. Bonding for even higher speeds is a challenge, but Adtran CTO Kevin Schneider doesn't see any obstacles that will prevent practical deployment.
ITU's early press release promised a gigabit from G.fast but real speeds are currently 400-700 megabits. Cablecos Videotron and Suddenlink are beginning deployments of a gigabit (shared) over DOCSIS 3.0. Comcast and Cox have a prohibitively expensive ($700+) fiber gigabit home that today is a pr stunt. Both tell me that they expect DOCSIS 3.1 to inexpensively achieve a gigabit by late 2016.
The business side hasn't decided how to price the high speeds. A gigabit over DOCSIS 3.1 only costs between $1 and $3/month more than a 10 megabit cable line. With competition weak, I expect a much higher consumer price, however. Sharing cable works remarkably well; a shared gigabit will deliver 500+ megabits to any home that needs it 95+% of the time.
Paul Spruyt of Alcatel predicted G.fast bonding in an interview almost two years ago.