There’s a recent paper by Gonzalo Cerruela García, Irene Luque Ruiz, and Miguel Ángel Gómez-Nieto of the University of Córdoba, Spain on State of the Art, Trends and Future of Bluetooth Low Energy, Near Field Communication and Visible Light Communication in the Development of Smart Cities (pdf)
The paper explains how technologies (NFC, BLE, VLC) will be important for the Internet of Things in smart cities and how they will need to be connected via LoRaWAN, Sigfox, Weightless, LTE, and 5G. With regard to Bluetooth LE they say:
Another challenge for the attention of BLE technology is the limited range problem; the range is directly dependent on Broadcasting Signal Power. An increase in signal power makes BLE devices less energy-efficient. Moreover it is necessary to improve accuracy in determining proximity to a BLE device.
The range problem will become less of an issue once Bluetooth 5 devices become available.