The update will be available OTA to owners of the dual-screen handset over a 4 day period, so if you don't receive it right away, there is no cause for alarm. Only 10% of Echo owners will have the software on August 1st. The Playbook even alerts stores to update demo devices to the latest software.
source: SprintFeed via AndroidCentral
The Sprint Playbook says that the Kyocera Echo will be upgraded to Android 2.3 over a 4 day period starting August 1st