The splits are kinda easy to think about now
Orcs-Troll-Tauren Horde
Human-Dwarven-Worgen Alliance
Goblins
Gnomes
Forsaken
Blood Elves-Dreanei-possibly Tauren Alliance of Light
Night Elves-otherwise Tauren-and also possibly Worgen Cenarion Circle
The Human and Dwarf close relations will never dissipate they are too developed and ancient that little diplomatic flabs wouldn't be able to ruin it. Its like the US-UK relations. Despite the Revolutionary War, War of 1812, Caroline Affair, and other minor 19th century events we are still as close as brothers.
Orcs and Trolls are in a similar situation. Vol'jin may disagree with Garrosh but we know that while he will not leave the Horde because Thrall asked him to trust in Garrosh at the same time he knows that if the whole war falls apart and if Garrosh goes evil Vol'jin will eliminate him and take the Horde over.
Gnomes are a picky they might remain with the Humans and Dwarves but at the same time the Gnomes did move out of IF because the regaining of their home and the Council of Three Hammers was complicating relations with the Dwarves.
Forsaken are an easy and obviously on their own
Dreanei and Blood Elves are currently the closest cross faction relationship that exists in WoW right now. The BE are indebted to Velen and his people so much it aint funny. The BE also seem to be focused and set upon changing their society from a magical one to a Naaru Holy Light one and that is why I have them classified as an alliance. The Tauren are tagged on because of their new Sunwalkers and a probable growing relations with the BE. While yes the Sunwalkers are not a majority nor are they shaping the politics like the Blood Knights are they are starting new ground and their ties to the light would set up more warmer relations then how the two started off.
Worgen and Tauren have multiple places they can end up. I already explained the Tauren in the BE-Dreanei alliance as for the NE one its obvious that their relation with them is similar to the BE-Dreanei only I feel the former relations are warmer then the NE-Tauren. At the same time though they could easily form a union with the NE based on the ideals of the Cenarion Circle. At the same time relations with the Horde are also very warm and so its possible they would never leave. As for the Worgen their close ties to their Human relatives is pure reason for why they might stick with Stormwind. otherwise we all know that the developments with Gilneas and Darnasus are reason enough for their union with the NE.