The US mobile operators are facing a critical turning point – one which many MNOs in developed markets will also face in the coming two years. Their traditional business models are collapsing, with the end of handset subsidies and device lock-ins, and the saturation of the postpaid smartphone base. Handset makers will increasingly sell directly to consumers (see separate item below), which also means the operators will lose their control of the software platform and user experience. At the same time, they are facing a second wave of intense network build-out, densifying their LTE networks in order to maintain a strong quality of experience (now the number one reason to choose, or leave, a network, according to Verizon, rather than…