I think Sky are already on IPv6, at least my Ubuntu box was grabbing updates from IPv6-addressed repositories last night.
And Virgin Media will do it when and if they can be bothered... so sometime in the mid 2020s no doubt...
I gave up waiting for my isp (plus.net) to roll out ipv6 years ago and went with a HE.net tunnel. Altho if BT are now rolling it out maybe there's some hope plus.net will also do it in the near-ish future...
so BT have already been screwing this up for a couple of years, thanks to Project Managers etc. Watch out for a Christmas of no internet for BT and LLU users.