If we assume economies of scale, eventually, it may become silly for a business to own lots of IT infrastructure. Why not lease it from cloud providers? They'll be able to do it cheaper, and besides…they’re experts. I think it’s possible that businesses will eventually migrate most (if not all) of their applications to the cloud.
The connection between your office and the central office is what we call the last mile. The last mile, at least in the US, has one big problem: it’s often owned by a single organization.
My interpretation of the SD-WAN value prop can be boiled down to cost savings, simplified operations, and improved application performance over inconsistently performing WAN links. Here's the conundrum. An engineer might instinctively recoil at this sort of value proposition.