By the time LTE is out, WiMAX 802.16m will be available, which is spec'd technically to 1Gbps, way higher than LTE. Only Sprint has enough spectrum to do it. But backhaul will be the challenge for ALL 4G carriers. We'll be lucky if 100Mbps is broadly available to every user at every 4G site in 5+ years.
Backhaul will be the limit, not the 4G technology.
