I think that everyone(or at least a big part of the whole community) would like to see class skins, such as Green Fire quest for the warlocks.
There are plenty of options:
-Dark Ranger for Hunters,
-Necromancer for DK/Demo Lock(?),
-Shadow Hunter for Shamans,
-Blade Master for Warriors,
-Blood Mages for Mages,
-and plenty more
The games has changed. So I guess it'd be actually understandable to expect DLC from WoW in the future, especially that it was bought by Microsoft. It wouldn't hurt the gameplay, because it's just cosmetics.
So... Would you buy DLC Class skins? Why? Why not?