Not in America
It's considered a felony and or a minor crime in America in all 50 states.
However some places it is legal in;
Eritrea
Egypt (Up to 4 wives)
India (For Muslims Only)
Iran (Up to 4 wives)
Libya (Up to 4 wives)
Maldivies
Malaysia (Strict requirements)
Morocco (Muslims only)
http://en.wikipedia.org/wiki/Bigamy
I wanted to find some more information regarding polygamy and I found this interesting map:
http://en.wikipedia.org/wiki/File:Le...f_polygamy.png
It would seem that the majority of the world considers it either highly illegal or or you'll be so shunned that it may as well be. This is a completely different situation than bringing up your equal rights comparison to same sex eternal bonding. Given this kind of situation, SE would face a boat load more critism than they would for the same sex bonding. Given that, the chances of it happening is slim.
Why can't I dress in woman's clothes in the game? SE, you're denying your cross dressing audience privileges and excluding them from how they want to play the game!
Why can't I marry my chocobo? I've spent more time with him/her than with my FC! SE, you're denying your bestiality ...er, I mean animal loving audience privileges that other couples have and I can't play the game how I want!
Why haven't I been anal probed by aliens yet? It happens in real life, so it should be a real possibility in Eorzea! SE, you're spitting in the faces of all those you DON'T THINK have been abducted by aliens and making a mockery of us!
Shall I go on? Because when else is SE gonna cave to our absurd requests? No time like the present, as was stated earlier.
And don't judge me because you can't see it from MY point of view!
I want to be able to marry my Minions, or Eos. I demand equal rights. I love dem pets dammit!
While this is a good idea to make our other friends happy so you dont have to pick one and the other will be hurt. I can also see this as a epeen brag with how many partners you have.. Tough choice but ill have to hope this doesnt get implemented
while the Miqo'te lore fits "a bit" this idea, Eorzean's lore is more about :
=> prostitution
=> harems
For both of them, you do not need to marry them.