"Do you think the new owners will invest in extending the network"
Minimally, the time is rapidly approaching when the way we recieve data will no longer need cables copper or other wise.
4g is here, 5g is already in the pipline, so it wont be long before all data can be streamed and recieved at acceptable speeds via mobile connections and that includes TV.
so unless they come up with some new reasons for people to keep paying around £13 and steadily rising per month for a phone line and then whatever else on top for B/Band etc they wont want to be spending money on a diminishing useage system.
For most people the B/band itself is pretty damn cheap its the cost of the needed phone line that bumps it up, so the sooner that these are removed from the equation the better.
for a lot of people the line rental is far more than their Broadband ! you can thank BT for that and their protected monopoly infrastructure paid for by taxpayers many years ago.
most of us would have had far superior Broadband years ago if it wasnt for BT.