On June 24th at 3:00 PDT for NA, 5:00 GMT for EUW, and 2:00 GMT for EUNE, servers will go down for maintenance and the 5.12 patch will be applied.
"On 06/24/2015, starting at 01:30 PDT, ranked queues will be disabled in preparation for patch 5.12. At 03:00 PDT, 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."Be sure to check your particular servers status page for your region's specific 5.12 maintenance times:
I'll keep you updated as more information on what the patch contains and patch notes become available. While the [ 5.12 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.