According to a leaked internal communication screen shot, Sprint is going to increase it's upload speed for the 4G networks to 1.5Mbps. This is available for both single and dual mode devices.

The increase is not a stabilized one which means you may notice a reduced speed during the peak hours. How ever they are keeping it as a secret as the speed increase is available only for the 4G devices.

See More: Sprint increasing the 4G upload speed to 1.5 Mbps