What's new in Warlords of Draenor?
Warlords of Draenor, the highly-anticipated expansion for World of Warcraft will be released on November 13th as you already might know.
Patch 6.0.2 (also known as the expansion pre-patch) is currently being tested on PTRs (Public Test Realms). This patch will go live approximately one month before the expansion.
This article represents a summary of the most crucial changes and new features that come with Warlords of Draenor.

The leveling cap
has been increased to Level 100.

Incoming Stat Squish
Character stats have been squished into smaller numbers. To set an example, you no longer have a million hit points, or deal damage in millions. This is not a nerf as enemies' stats have been reduced as well (mobs have less hit points, do less damage).

New Talents
A new row of talents has been added which you unlock upon reaching Level 100.
New perks exclusive to Draenor are earned every other level from 91 to 100.

Miscellaneous
-Garrisons are a new feature, exclusive to Draenor, where you'll build your own base, recruit followers, send them on missions and collect rewards.

-The functionality of Agility, Strength and Intellect has been balanced.

-New secondary stats are added: Bonus Armor, Multistrike, and Versatility.

-Hit and Expertise have been removed! Your attacks will reliably land without them.

-The pacing of healing has been adjusted,to allow amore tactical decision-making approach, regarding efficiency and throughput on both single/multi-target heals. Passive and auto-targeted healing have been reduced in effectivenesss that actions and choices of healer's are emphasised.

-Some instant healing spells were given cast times.

-Racials have been balanced so that there's equal combat performance.
All classes have had several abilities removed (the less-used ones).
The amount of crowd-control abilities has been drastically reduced. Some were removed entirely, while others have been merged together.

-All characters now learn some Major Glyphs during their leveling process automatically.

-Vengeance has been redesigned and renamed to Resolve. It does now increase tank self-healing and absorption based on damage taken.

-Facing requirements (positioning) for many spells has been removed or loosened.

-Mana cost of Resurrection spells has been reduced to make recoveries from a wipe faster.

-Professions no longer have combat benefit perks.

This concludes the most interesting changes brought in Warlords, below you'll find some reminders that may be relevant to you, before the game goes live.

Reminders
Challenge Modes that were added in Mists of Pandaria will be removed and their respective achievements will become Feats of Strength. New Challenge Modes and rewards are added in Warlords of Draenor.

Brawler's Guild Season 1 ends, all their respective achievements will become Feats of Strength. A new Season seems to be planned, but there are currently no more information about this from Blizzard. Maybe they'll add it in future content patches, such as 6.1.

Kor'kron Juggernaut's (Heroic Garrosh Mount) drop rate will become rare. Currently, it's guaranteed on Heroic difficulty.

Wrathion's Legendary Cloak Questline will be removed. All in-progress quests will be cleared from quest logs once Warlords hits live servers. Starting the quest line for new characters will be removed already in the expansion pre-patch. Only players that are working on the cloak currently will be able to complete it. To compensate, Blizzard has decided to keep the +100% Reputation Gained with the Black Prince active until Warlords, so players have a quicker chance to get their cloak.