Bandwidth is just one factor in validation.
Moore's law has actually begun to fall down in a number of ways (perhaps "storage" being the only one that now still stands even though initially it was only supposed to refer to computing power).
This has been in part due to the 3GHz limit that CPUs can operate at (without requiring seriously expensive cooling) and the fact that bandwidth has actually never even followed such a trend (instead it tends to jump every few years by quite a bit but then stagnate for quite a while after that).
Most improvements in processing speed these days are made through multi-threading (which can be applied to block validation) but that doesn't help when you are doing serialisation of information.