Many years ago we had Russians, Germans and French and others in the EVIL alliance, which worked pretty well.
That is actually what I´m talking about. I was in SIN for quite some time. I remember a few fights were the RUS guys basically did their own thing and no one could talk to them. It was kinda sad funny, since they usually just fought to the last man and then were kinda sad we left them to die.
ES had the same problems from time to time when they had no one online that would speak adequate english.
I think it´s good that there will be national guils, they add a certain spice to sandboxes and I´d rather have more players than less. The only thing that suffers a little is roleplay, but then you can always pretend they speak some kind of dialect no one understands.