The new expansion promises a lot of new content, but besides the changes to the world itself (and being able to finally fly around everywhere!) the most exciting feature is the changes that encourage people in a guild to work together for shared rewards.
Initially there was going to be a talent tree associated with the whole thing, but the developers made a very wise and removed it. Why would you want to limit your decisions to just a small group of people (do we take things PvE or PvP… do we get this rewards that benefits this 10 people or this 50). Now the rewards are more across the board and I think this was a great axe to something that could have created guild hoping until people found the right set of rewards in a guild.
Professions is something that I did not get into until recently and I between the wife and I we are getting close to having every single profession in the game maxed out. The guild has strong crafters in every spot. From Moon now having every single epic gem pattern in the game, to a couple of our inscriptionist having every singly glyph not to mention enchanters with even the hard to find ones. We will enter the new expansion with people not just eager to conquer new content but also max out their profession and this time the guild will benefit equally from both.
It seems that besides killing Arthras a lot of people are preparing alts to take even possibly a center stage in the next expansion. It provides a great opportunity for you to make an alt your main and enjoy that new content from a different perspective. I am personally very excited about the disc priest being rewarded for DPSing! I cannot wait to start stacking smite and getting benefits from it!