AT&T is undergoing a radical slimming-down operation, in a bid to reduce costs which may, some sources say, jeopardize elements of its migration to a fully virtualized, software-defined and open 5G and converged network. Of course, some of its strategies, such as migrating non-network applications to the public cloud and opening up the supply chain, are designed to reduce total cost of ownership as well as enable new services. But a cloud-based network vision of the kind outlined in the past by AT&T leaders like John Donovan takes significant time, risk and upfront cost, and involves many partners and integrators – all of which may see AT&T diluting its ambitions somewhat during its current focus on efficiency. In the near…