If you think fibre will be outdated in 20 years, how long do you think it will take copper to be outdated.
There is zero reason for fibre to be outdated (it has enormous untapped capacity and the speed of light), and as what gets bolted to the ends of the fibre makes it go, the technology changes will be updated at the fibre ends.
Why would you think fibre would become out dated, if you believe some, households don't need any where near the capacity of fibre, and obviously the radio spectrum is limited and will never be a viable alternative to replace fixed line.
