That what all the Tech's told me. 10-25 years.
Cable TV did try and quit a couple years ago. Step in my area, and you will think you went back 50 years. Miles of Corn with nearly a neighbor in sight.
Digital wires in 15 years. Thats the estimate, I got from a tech friend for sprint. That services our area. I tried IDSN and was slowed down to "dial-up" speeds. Due to our archaic copper wires.
And in my area there is little demand for "Broadband". One tried a years ago and quit. Out of 1000 people called in my area Me and five people stated they wanted Cable Broadband. The rest stated "no".
Wireless though might be something to look into though in a couple of years.