No no no. Remember that factions are a “pillar of WoW”… Until Baine feels guilty and breaks out a prisoner to help out an Alliance NPC, or Alliance NPCs decide to group up to go break Baine out of a Horde jail cell, or Anduin strikes up an allegiance with Saurfang to help sort out the Horde’s issues.
It is a true staple of PvP as well… Unless one side has queues that are too long then a player can hop over and fight for the other team, or in rated PvP it doesn’t even matter because factions can fight their own factions.