Based on the way Bungie has designed Destiny so far, and common sense, the answer is "No". Most likely, even the act of joining a Faction probably isn't a permanent one. Think about it this way: If joining a Faction was a permanent event, then Bungie is effectively splitting up the playerbase into 5ths, which would be extremely disruptive towards community building. "Hey, you seem like a cool guy, do you want to play under the New Monarchy Banner tonight?" "Sorry, my main is Dead Orbit, my New Monarchy Character is bad." "Oh, I don't even have a Dead Orbit Character. That sucks." From everything we've seen, Bungie doesn't want players to regret the choices they make in Destiny. There are no race attributes, because they don't want a situation where you make an Awoken Titan only to figure out three hours in that it would have been better for you to make an Exo Titan because their racial bonuses match up better with the Titan's. And even with classes, there's a ton of overlap between what the classes can do, so even then you won't pick a Warlock and then be left completely cursing your decision down the road. Factions would be no different in my mind. It would suck to join FWC only to figure out that all your friends joined the Seven Seraphs. I imagine Factions are just a hat that you wear depending on your mood. People can certainly have their favorites, and deck their stuff out with the appropriate symbol and colors of their faction, but I can be a diehard Osiris fan one night and then join a friend for some New Monarchy shenanigans the next. I would be very surprised if Factions were mandatory, and if they were permanent choices.