NBASE-T pushes the limit on most aging cabling infrastructure for supported devices.
Initially conceived as a way to deliver over gigabit speeds to newer 802.11ac Wave 2 wireless devices over Cat5e and Cat6 cables, this technology may change much more. 802.11ac Wave 2 can deliver 6.8Gigabits per second, but Cat5e-Cat6 cabling is traditionally rated to only deliver 1Gigabit/second of data.
NBASE-T will be able to increase the speed of devices capable of the technology up to 2x, 5x, and even 10x the speed depending on cabling type, interference, and continuity using existing cable infrastructures.
In ideal conditions:
Cat5e will be able to hit 5Gigabits/second.
Cat6 Will be able to hit 10Gigabits/second at 55meters or less, and 5Gig otherwise.
Cat6a will be able to hit any of these speeds.
If the lengths and interference on the lines won't deliver the ideal specs the protocol will autonegotiate to the next highest speed it can. SO even for a long interfered run, it may be possible to get 2Gigabit/second on an old Cat5e line.
This new technology will significantly improve preexisting infrastructures who aren't looking to remodel and rewire right now, simply by purchasing equipment, new network devices and cards that support it. Flexing this new tech is not just limited to wireless access points either; we are already seeing some Network Interface Card (NIC) manufacturers rapidly adopting it!
More info:
http://www.nbaset.org/
https://twitter.com/NBASETAlliance
https://meraki.cisco.com/technologies/multigigabit
http://www.cisco.com/c/dam/en/us/solutions/collateral/enterprise-networks/catalyst-multigigabit-switching/multigigabit-ethernet-technology.pdf
http://www.nbaset.org/intel-nbase-t-enterprise-networking-solutions-at-cisco-live/