With 10.1's xfaction guilds - do races or the game need to be tied to 2 factions?

[Soon-TM]

It's just down to gameplay.
Guilds aren't lore based. Their will always be a Horde and an Alliance.

Guilds will just be an in-game mechanic where players can just play whatever they want. If somebody hated Troll Druids and wanted to be a Night Elf Druid and still raid, they can do that. Likewise, if somebody didn't want to play a Night Elf Priest anymore and really wanted to play a Blood Elf Priest for raiding, then that can happen now and still be within the same guild.

Perhaps RP'ers are happy with this change as well

It also should prevent Hackuser from villain-batting the Horde a third time, if only because a MoP 3.0 (or rather BfA 2.0) would be quite hard to pull out with crossfaction guilds as a central feature. Although who knows... Third time's the charm

[Schizoide]

Sure, several games have "betrayal" quests allowing you to switch factions. Everquest 2 comes to mind. Only caveat is PvP. Instanced PvP you can just be in disguise, mercenary mode or whatever they call it, but world PvP is a bit of a quandry. My feeling is most people just see a red name and don't care or notice the race, so it wouldn't be a big deal, but I'm not a PvPer.

[huth]

Sure, several games have "betrayal" quests allowing you to switch factions. Everquest 2 comes to mind. Only caveat is PvP. Instanced PvP you can just be in disguise, mercenary mode or whatever they call it, but world PvP is a bit of a quandry. My feeling is most people just see a red name and don't care or notice the race, so it wouldn't be a big deal, but I'm not a PvPer.

In Arena, you can easily end up fighting your own faction. I don't think it's really much of an issue. Just have people pick a faction when turning on Warmode.

[Schizoide]

Sure. I didn't want to make that call simply because I don't PvP and don't want to speak from ignorance.