The problem isn't that Ethernet needs to go away - the problem is that RJ-45* is a huge plug for 8 tiny wires.
USB 3.0 cables have 8+ pins and USB 3.0 Micro-B connectors are tiny compared to RJ-45.
The pins in an RJ-45 plug are laid out quite efficiently - the problem is the rest of the connector is a big, useless hunk of plastic.
If IEEE and/or ISO can come out with a mini- or micro-Ethernet connector (which should be quite feasible), and the hardware companies adopt it, then we can have the speed and security of a wired NIC, without the ginormous jack that is currently needed for it.
This is, of course, until/unless Fiber becomes ubiquitous for (comparatively) short connections. At that point, Ethernet can die its quiet death. Until then, we will need a way to transmit bits over a copper-based LAN, and Ethernet cables are the best choice for that - they just need a smaller connector to make them a better choice than the slower, less secure, less reliable wireless in ultrabooks.
*Yes, I know that Ethernet doesn't technically use RJ-45, but the two specifications are close enough to be irrelevant to the point that I'm making
Keep Up with TechRepublic