From the post Scotchka linked (EU version):-
Warfronts
- Arathi/Stromgarde rewards will remain as they were previously.
- Darkshore rewards will go up by 15 item levels, so that the outdoor world boss and the once-per-cycle quest both award item-level 400 gear.
- The power of all enemies in the Darkshore Warfront will also go up by roughly 15%, and the item level required to queue for Darkshore will go up from 320 to 335.
- Special note: The two Darkshore changes will only take effect after the current Warfront cycle has ended. So if Alliance is attacking Darkshore in a given region when Season 2 begins, and has 3 days left in that attack cycle, that Darkshore will still give Season 1 rewards.
- This is being done to avoid any unfairness to people who had already completed the Warfront or done the world boss just prior to the season rollover…
Dungeons
- The item level of rewards from max-level Normal, Heroic, and Mythic dungeons will go up by 30. Baseline rewards will be 340 from Normal, 355 from Heroic, and 370 from non-Keystone Mythic.
- Difficulty of Heroic and Mythic dungeons will also go up by roughly 30%; Normal dungeons are unchanged.
- Mythic Keystones will go down by an additional 3 levels when the season transition occurs, to account for this difficulty increase. So if you do an 11 this coming week, instead of getting a Level 10 keystone when Season 2 starts, expect a 7.
- Mythic+ rewards will also go up by 30 item levels; however, during the first week of Season 2, rewards from end-of-run chests will be capped at Mythic 6 quality (item level 385), and the chest you open next week will contain Season 1 rewards if you do a Mythic+ run this week. (So, for example, if you do a Mythic 10 during the final week of Season 1, you’ll get a Season 1 item level 380 piece and 60 Residuum from your first Season 2 chest.)
- The weekly cache that becomes available in the second week of the season will not be affected by this cap, so if a player does a Mythic 10 dungeon during the first week, they will get a Mythic 10 reward (item level 410+) from their cache the following week.
PvP
- Season 2 rewards from rated PvP sources are 30 item levels higher than they were in Season 1, including Conquest rewards and the weekly chest.
- End-of-match rewards will be capped at 385 during the first week of the season, to maintain parity with other endgame systems until Mythic Battle of Dazar’alor becomes available.
To be honest you might as well read the whole thing 