Clearly, there is pent-up demand from US businesses and consumers for such high speeds, but AFAIK the country's long-haul and last-mile infrastructure is nowhere near ready for handling end-user traffic at 400Gbps, let alone 1Tbps.

On the long-haul side, service providers like Level 3 Communications appear unlikely to invest aggressively to add a lot more capacity any time soon, because they are still dealing with the financial consequences of their over-investment during the 1990's telecom boom (remember Worldcom?). On the last-mile side, service providers like Comcast also appear unlikely to invest aggressively to add a lot more capacity any time soon, because their traditional business models are under threat from companies like Netflix -- our last-mile providers fear higher speeds.

So, we have demand for ever-faster speeds on one hand, and constrained supply on the other hand. Economics 101 suggests Internet service pricing is bound to stabilize or even (gasp!) increase over the coming years.