Just to clarify BT's FTTC will not be 400Mb/40Mb by 2017. The current FTTC product might be in the 100Mb/30Mb ballpark but cannot go to 400Mb.
This will be a new product using the new standard G.fast. BT have not announced any details of the download or upload speeds they plan to offer on the newer standard they'll be rolling out, beyond that they plan on offering 500Mb to 'most' homes by 2025 and will start in 2016-17, with the hope of offering 'a few hundred' megabits per second to 'millions' of homes and businesses by 2020.
Things will be clearer when they have done the trials. As this is brand new technology BT do not know what it's capable of when rolled out to any kind of scale - no-one does yet as it hasn't been rolled out to any kind of scale yet, so it won't surprise anyone to know that 400Mb/40Mb was a number picked out of the hindmost and, regardless, the upload speed will be way higher than 10% of download in any event.
http://home.bt.com/news/bt-life/bt-c...11363958493131
VM will be at gigabit speeds, if necessary to compete, by 2020.