"Gigabit without a backhoe. ... We don't have to dig up the streets and can go incredibly fast. You're going to see us go coast-to-coast in the next 12 months," Comcast CTO Tony Werner tells Amy Maclean in a short but important interview. I'm told there are unannounced Comcast deployments of DOCSIS 3.1 in Chicago and California, as well as the large public trial in Atlanta. I'm guessing that Comcast has already upgraded the CMTS for millions of lines, ready to turn on large systems when they believe everything is ready. (That's consistent with what manufacturers are shipping but I don't have confirmation.)
Cable supplier Arris expects substantial sales of DOCSIS 3.1 modems starting early next year, which is consistent with Tony's prediction. Note that the high speeds are likely to be download only. Upload looks mostly to be 90% slower.