Answer to Midi-DSL, gets the promised gigabit. Bonding two - or ten - DSL lines has worked for years but most thought G.fast had enough speed bonding wouldn't be needed. A Google search +bonding +G.fast finds nothing. G.fast torchbearer Sckipio is discovering a need however, and now is promising to bond two G.fast lines to ~double speed. They've put "THIS YEAR" in capitals because apparently customers care. (see illustration.)
Bonding may prove important at both the high and low end of G.fast performance. Promising a gigabit from G.fast got the ITU committee headlines around the world but trials aren't delivering that speed. Cable is now available to half a million French homes at 800 megabits (shared) and soon will be a gigabit in many places. There may be no practical purpose in speeds over 100 megabits or so but Google in Kansas City is proving customers like the gigabit.
The speed doubling may be more important protecting the low end of G.fast.
Alcatel is getting interest from telcos who want high speeds at 200-500 meters. They've proposed Midi-DSL, extending VDSL to 35 MHz and tweaking things. G.fast torchbearer Sckipio is answering back with G.fast demos of 400-500 meters. Speed falls, but 100+ megabits is promised. Alcatel says the Midi-DSL will be faster at 400 meters and bonding to double speed would be a natural response by Sckipio.
It's unlikely bonding will actually be used for many lines, even if offered. Telcos may want an advertised answer to high cable speeds but will generally avoid actually selling it. It would require a technician to make a non-standard installation and add complexity. They will probably discourage actual orders with a high price.