Wireless may be very useful and yes speeds are increasing but it can never form the backbone that is needed to keep our communication network standing.
It is basic physics. To send data over wireless connection at the same capacity as a fibre connection would take an enormous amount of energy. Energy that at radio (wireless) frequencies is pretty close to microwave bands. So imagine beaming all that energy around the place will soon clog up the spectrum, not to mention the heat radiation of everything that absorbs the wireless signal.
Fibre is expensive, but scalable and future proof. Wireless is a technoloogy that goes though updates every few years, leaving behind it incompatible, insecure and obsolete devices. And we can't sustain the mythological 1Gbps wireless speed because we'd all be fried from the energy required to sustain it. As mentioned, wireless requires lots of broadcast towers, that are also not scalable or sustainable in the long run. A fibre run can be left in the ground (dark fibre) until it is needed. If we require a doubling of the capacity, then add a dark fibre bundle. And the switch technology can be upgraded without having to pull out all the fibre.