Now that Night Elves and Humans are literally neighbours, they'll definitely share a lot more of their cultures and knowledge than previously.
All I hope is that Night Elves to investigate Everbloom Portal south of the Mage Quarter and somehow develop not-so-Scourgey Botani / Ancients to increase their military power / provide us a choice of plant-based race.
Furthermore, just like how Delas Moonfang has become a Paladin, maybe they will open up Night Elf Paladin class, and Humans to Druid and etc, to show the evolving influences in the racial dynamo and relationships.
For the Horde side though, I seriously have no clue how can the Forsaken influence / be influenced by the other Horde members, but I hope there can be some interesting interactions and mixes between these groups as well.
What do you guys think?