On August 13th at 3:00 AM PDT for NA, 5:00 GMT for EUW and 02:00 GMT for EUNE, servers will go down for maintenance and the 4.14 patch will be applied.
Here's NA version of the Network Operations maintenance announcement:
"Server Maintenance: Patch 4.14 On 08/13/2014, starting at 1:30 AM PST, ranked queues will be disabled in preparation for patch 4.14. At 3:00 AM PST, the servers will be shut down and all games currently in progress will end in a draw and stats will not be recorded. We estimate the battlegrounds will be unavailable for 6 hours."Here's a collection of the patch 4.14 maintenance threads for each server:
I'll keep you updated as more information on what the patch contains and patch notes become available. While the latest PBE content is usually a good indicator of what's to come, please remember that it is tentative and not everything may make it to live. Be aware the SR update and the launcher/client visual refresh will NOT be in 4.14.