On January 28th 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 5.2 patch will be applied.
"On 01/28/2015, starting at 01:30 PST, ranked queues will be disabled in preparation for patch 5.2. At 03:00 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."Be sure to check your particular servers status page for your region's specific 5.2 maintenance times:
I'll keep you updated as more information on what the patch contains and patch notes become available. While the 5.2 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.