'Course there is also the issue of timing. Would a punter be happy just to be told that the ADSL service will cease, and VDSL begin at 'some' point during a specified day ?
As Gazter has already pointed out, since ADSL went self install way back when, I have spent many years politely showing punters that they have set it up wrong, or that internal extension wiring is having a detrimental effect on the service. The faster it goes, the worse the internal wiring
It will come, but it's going to cause grief.