Coming tomorrow to the US and the day after on EU, Wowhead gathered up all the fragmented info from the patch notes and later class updates from the forums, so check them out.
Blizzard have finally shared the timing of 7.1.5's release and, as expected, it's coming a week ahead of Nighthold. This gives the top guilds a bit of time to prepare, check out all the class and legendary item changes and adjust raid compositions for that Mythic January 24th showdown to end all showdowns. Well, for tier 19 anyway. Here's the official release date announcement, complete with video survival guide and patch highlight previews:
We’re ringing in the new year with a brand new patch on Tuesday, January 10. Patch 7.1.5 offers a variety of new content, including a new Timewalking event, Micro-Holidays, and the return of the Brawlers’ Guild. Dive into our previews and developer Q&As to learn more about each of them.
Live Developer Q&A's