On March 12th at 3:00 AM PST for NA, 5:00 GMT for EUW and 02:00 GMT for EUNE, servers will go down for maintenance and the 5.5 patch will be applied.
"On 03/12/2015, starting at 01:30 PDT, ranked queues will be disabled in preparation for patch 5.5. 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 5.5 maintenance times:
I'll keep you updated as more information on what the patch contains and patch notes become available. While the [ 5.5 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.